This is the second section of my electrical system upgrade. You can read the first part, how to upgrade the OEM ground wire, here.
This how-to will be covering the details on how to perform the upgrade known as the ‘Big Three’. Essentially, it will yield the following:
1) Reduced dimming and smaller voltage drops 2) More stable voltage and better current flow 3) Less strain on your vehicle’s charging system
The BIG THREE consists of:
(1) Battery negative to chassis (2) Alternator to battery positive (3) Engine Block to chassis
…it essentially does the same thing as a conventional grounding kit, however, it does so in a different fashion. I am not a big fan of grounding kits as I prefer this method. People will argue this one way or another, but I swear by this. So, let’s get started!
TOOLS/SUPPLIES
10mm Socket
12mm Socket
Ratchet
10ft. of 1/0AWG Power Cable
3 1/0AWG Ring Terminals
1 1/0AWG Fuse Terminal w/ 300-amp fuse
STEP I – BATTERY NEGATIVE TO CHASSIS Simple enough. We are going to be making an attachment from the negative terminal of the battery to the chassis. If you peek behind the battery you will see a good place to plant the wire.
Remove the bolt with your 10mm socket and sand away the spot to bare steel. After that, attach about a 1-ft. length of wire to one of your terminals, crimp, and bolt everything back together.
STEP II – BATTERY POSITIVE TO ALTERNATOR POST
Alright, this one is a bit more tricky. You are going to need about 5ft of wire split into two equal 2.5ft. lengths. We are going to be attaching the wire to the battery positive to a fuse terminal, then fuse terminal to alternator post. You can find the alternator just to the outside end of the engine block on the passenger side. Look for a rubber boot covering a bolt. That’s your alternator post. We’ll start there. Remove the bolt using a 12mm socket.
Attach one crimped end of the 1/0AWG wire to the bolt, then screw everything back together.
Take the lead attached to the alt. post and run this to the fuse. Take the other length of wire and run this from the opposite end of the fuse and lead it to the battery. We’re almost done!
STEP III – ENGINE BLOCK TO CHASSIS
The final step is simple enough. Start off by locating a spot where you want to land the lead on the chassis. I chose an empty bolt hole located by the engine block. Sand away as we have done before.
Next, simply ground this to the engine block. I chose one of the 10mm bolts located on the side of the block. You can choose just about anywhere on the block; for instance, you will see two grounding points on top of the block. Golden rule with grounding wires is to keep them as short as possible, so just keep that in mind when doing this…
…and now you’re done! Here’s a shot of the battery when all is said and done…pretty bada’ss if I say so myself!
The 5th Generation Maxima is a very reliable car – if you know how to maintain it. The problem is that the car suffers from a few design defects that can make it expensive to maintain. For example, a worn-out engine mount may damage the Engine Control Unit (ECU) resulting in a major inconvenience and a dealer repair bill of $2,000-$4,000. Other actuators may fail with similar effect, sometimes repeatedly.
This note describes these problems and the remedies for eliminating them. The remedies are inexpensive and easy to do. If you own a 5-Gen Maxima, I strongly suggest that you do the following as soon as you can:
Implement “Coolant Bypass”, or replace your Idle Air Control Valve (IACV), or both.
If your car has an Automatic Transmission, then disconnect your two electronic engine mounts, both front, and rear.
Replace fuse #58 (15A, labeled ENG CONT1) in “Fusible Link and Fuse Box” by the battery with a 7.5A fuse.
Do the above even if your car experiences no problems at this time. If your car already experiences problems such as P0505 or damaged ECU, then read this document before attempting any repairs.
The above instructions may not make much sense unless you understand what the problem is. The next section describes the problem, and the subsequent one explains the remedies in more detail. If you own a 5.5-Gen Maxima, keep reading but you can dismiss the IACV issue – your car does not have an IACV to worry about.
Problem Description
The fundamental problem is that in the 5-Gen Maxima the Engine Control Unit (ECU) is not properly shielded from the failures of some components it controls. For example, we know that the ECU can be damaged by a) Failed/shorted IACV, and b) Failed/shorted Electronic Engine Mount. There are also some reasons to suspect that failure or misadjustment of the TPS (Throttle Position Sensor) may have a similar impact; I am still investigating.
How the IACV Fails
Most often, the IACV fails after the engine coolant1 shorts the wiring in its stepper motor. There is an O-ring gasket that should prevent the coolant from getting into the IACV, but after 10-15 years, it tends to fail. I suspect that there are other reasons why the IACV fails. For example, the thermo-valve inside the IACV may get stuck, or there is an intake leak; the IACV then tries to correct and eventually fails. The bottom line is that IACV failures (code P0505) are reasonably common and that they have disastrous consequences.
1 Engine coolant circulates through the Throttle Body and IACV to eliminate potential starting problems in cold weather. However, this seems unnecessary as the TB/IACV is nicely hidden between the two engine banks. There are multiple posts on maxima.org that confirm that there are no starting problems with coolant bypass, even in Minnesota winters.
Poor Fusing Protection of the ECU: When the IACV Wiring Fails and Shorts, 15A Current Flows Through the IACV and Damages the ECU Figure 1
Figure 1 illustrates how the damage occurs. With a healthy IACV, the resistance of each IACV half-coil is 22 Ohms. Together with other factors this limits the maximum current through each half-coil to 0.5-1.5 Amp, and to a maximum of about 3-3.5 Amps through each of the two ECU ports and the STA509A transistor behind each port.
When the coolant eats up the insulation, the coil shorts, and the resulting current – up to the 15A limit imposed by fuse #58 – will flow through the IACV and “fry” the ECU. The 15A fuse should blow out, but usually the STA509 driver transistor in the ECU burns first, sometimes taking adjacent components with it. Appendix A shows how a damaged ECU looks like.
The horror story does not end here. Typically, the result is that both the IACV and the ECU aredamaged. If the owner replaces just one of the two parts (say, just the ECU), he will find out that his new ECU is immediately damaged by the IACV he hasn’t replaced yet!! Even Nissan dealers are known to have made this mistake! The bottom line is: Make sure both parts are OK before replacing either!
Failure of the Electronic Engine Mount
5-Gen Maximas equipped with an Automatic Transmission have two Electronic Engine Mounts (Rear by the firewall, and Front by the radiator). Figure 2 shows the wiring schematic for these two mounts. Again, failure of either mount can damage the ECU in the same manner that the failure of an IACV can.
Poor Fusing Protection of the ECU: When an Electronic Mount Fails and Shorts, a 15A Current Flows Through the Mount and Burns the ECU Figure 2.
Each electronic mount has two states – Firm and Soft. Normally, the ECU puts the mount into the soft state at low RPMs (below 1000 RPM) and into the Firm state when the engine runs above 1,000 RPM. Disconnecting the mount eliminates the danger of ECU damage. It has no effect on the car (no codes or SES light) apart from occasional vibrations; more on that in the “remedies” section.
The Remedies
The ideal remedy would protect the ECU by using onboard fuses on all its critical inputs and outputs. However, I rejected this approach because of its risks: adding components to the ECU board and cutting traces or modifying wiring is just too dangerous for the average Maxima owner. For the same reason, I also rejected any solution that would cut/modify the Engine Room Harness.
This left me with the remedies described below. All of them have been successfully tested by the author.
Remedies for IACV Failures
There are three remedies that will reduce the probability of an IACV failure:
Preventative IACV Replacement. It seems that most IACV’s fail at around 100-120k miles. To replace your IACV, you have to remove the Throttle Body and unscrew the four Phillips screws holding the IACV. This is not a pleasant task, as the screws tend to be frozen. Once the job is done, a new IACV (use OEM part only) should be good for another 100K miles or more.
Coolant Bypass. Coolant Bypass (see figure 3) eliminates the possibility that your engine coolant will eat on your IACV wiring. On a 2000 Maxima, the bypass requires no additional parts – neither hoses nor clamps – apart from a good set of hose pliers. The job can be done in about 5 minutes (excluding the access/re-assembly time), with the Throttle Body in place. When you do the bypass, remember to blowout any residual coolant so that the IACV is as dry as possible. Also note that in a departure from figure 3, you can completely remove the IACV “half-hose” leaving the two coolant orifices on the IACV open.
Implementing Coolant Bypass: No Parts Required, Just Move the Hoses Around Figure 3.
ENG CONT1 Fuse Replacement. Replacing fuse #58 (15A, labeled ENG CONT1 in the Fusible Box next to the battery) with a 7.5A fuse provides an improvement over the OEM setup. Be aware that the 7.5A fuse does not guarantee protection: The STA509A transistor can be damaged by any current exceeding 3A (see footnote2), but the fuse needs to be larger than 3A because there are multiple devices on it3. However, going with the smaller 7.5A fuse increases the probability that the fuse willblow before the STA509 transistor will, and it decreases the probability of large-scale damage – such as burned traces – to the ECU board itself! The fuse costs a few cents (http://www.delcity.net/catalogdetails?item=77075) and can be swapped in/out in 30 seconds.Important Note: If/when the 7.5A fuse blows, you need to treat it as a signal that your IACV has failed. You should check the IACV, and if indeed shorted, replace it.
To summarize, there is no reason not to do #3. The same applies to #2. So, the question is: After you are done with (#3 + #2), should you do #1? I have done it eventually when my IACV experienced other problems (needed cleaning).
Isolating Engine Mount Failures
Only AT Maximas have Electronic Engine Mounts. For these cars, the following remedies exist:
Disconnect Electronic Mounts. Disconnecting the Electronic Mounts is the quickest solution. The connectors are brown, each with 3 conductors, and both are located close to the AT dipstick. Depending on whether the mount is disconnected in Firm or Soft state, you may experience the following side-effects: A: Mount in Firm State: Some/minor vibration when the engine idles. B: Mount in Soft State: Minor in-line vibration between 1,800 and 2,400 RPM, when the engine pulls, only under some conditions, depending on how you step on the gas. I suggest you do not worry about the Firm/Soft state too much: once disconnected, the electronic pump within the mount will stop firming up the mount, and the mount is bound to become (semi)Soft no matter how you disconnect it.
Replace with Manual Mounts. Using the mounts from MT Maxima is possible. It is also relatively easy as the MT mount is a direct fit. This is the preferred solution when the original mount is physically worn out. The side-effects are the same as in (1a) above.
Add a Fuse to the Mount. It is physically possible to add a fuse to your Electronic Mount. The logical place is at connector terminal #3 where the battery power comes in (see figure 2). However, this would be best done when the mount is being replaced. Otherwise, #4 below may be a better choice.
Non-ECU Control of Electronic Mounts. Yet another solution is to keep your Electronic Mounts, but take the ECU out of the loop. One would have to implement a semi-intelligent control that is both fuse-protected and decoupled from the ECU (or any other expensive part). I am tinkering with this solution.
2 Each of the two IACV half-coils is powered by a single STA509A transistor within the ECU. Each transistor can withstand a maximum current of 3A in steady-state mode and 6A in pulse mode. The desired protection would insert two fuses – one into the lead/connector port #2, and one into port #5 of the IACV (see figure 1). It would allow for proper fuse sizing, somewhere in the 3A-6A range for each fuse.
3 Powered off this fuse are multiple subsystems: IACV, EGRC1, MAFS, TP/SW, and others.
Repairing vs. Replacing Your ECU
ECU failures are annoying and expensive. When the ECU can’t be repaired, the only solution is to purchase a “new”4 ECU and then tow the car to the dealer to have the keys reprogrammed. In some places, you may be able to find a locksmith that can do this task but it is not clear this is always possible. The key point is: because of the hassles associated with key reprogramming, you always want to repair your ECU rather thanreplacing it.
4 “New” means “appropriate ECU of the same type, in working order
The following outfits provide ECU repair and are considered reputable:
AvPro ECM in Fort Meyers, FL (http://www.avproecm.com/nissan.htm). These guys will not only repair ECU, but also they will also improve it by adding fusing protection. All this for $250, with 2-3 day return and a lifetime warranty. I have talked to them, and they know what they are doing (Update 7/19/2016: It appears these guys are no longer in business).
Directly or indirectly, many members of maxima.org (and Nakis in particular) contributed to this note. I have learned a lot from other MAXIMA.ORG members. This note is an attempt to re-pay some of my debt.
Appendix A – How a Damaged ECU Looks Like
The above pictures are just examples. Not all damaged ECUs look like this. Sometimes, a burning smell is the only indication.
Appendix B – Notes re. Improved Fusing
Existing fusing:
Fuse #58 covers, via ECM relay pins (#6, #7), the following: MAIN, MAFS, POS, EGRC1, EGVC/V, AAC/C, TP/SW, IGN/SG (acronyms from the FSM). From the circuit diagram, this is only:
IACV, EGR/C1, IGN/SG (Coils) – and nothing else; still, this is too much for a single fuse, so we must insert the fuse at F52 (the IACV connector)
Fuse #59 covers, via ECM Relay pins (#3, #5) the following: MAIN, MAFS, POS, EGRC1, EGVC/V, AAV/V, TP/SW, IGN/SG, EMNT, TPS, NONDTC, NATS. From the circuit diagram:
ECM pins 110+112, CPS-POS, MAF, TPS, EMNT,
Solution requirements:
Should be switched by ECU/other relays
Avoid cutting the harness!
Possible implementations:
Insert two fuses at IACV connector (F52). Insert them serially into IACV pins/leads #2 and #5. After splicing, bring the four “fusing” wires to some convenient place where the fuses would be placed. Use 3A fuses.
New Power Circuit for IACV. Bring two new power lines to the IACV (use fuse adapters to create them). Fuse them either after, or before, the ECU Relay. The latter case will only work if the ECIU relay has two spare pin(s).
I just swapped my Walbro 255 Fuel Pump to an AEM 340LPH because I wanted something better suited for E85. I also did not like the “whine” noise on the Walbro. The AEM 340 does not have the whining noise and works great. I also replaced my fuel filter. Nissan says that it is a “lifetime” part and never needs to be replaced. I disagree with that especially seeing how dirty and filthy my fuel filter looked. It’s very simple to change and the filter costs less than $30 bucks. This is just a reference post and not really a how-to on the AEM pump
Fuel Pump Part Number: 50-1200 (Price – $116.00) Fuel Filter Part Number: 16400-2Y505 (Price – $25.00) Fuel Pump Sending Unit O-Ring: 17342-01A00 (Price – 16.00)
New OEM Filter vs Old Filter (Likely never been changed)
I cut the old filter so you can see how dirty and filthy it is.
My passenger side axle was bad. It was aftermarket but not sure of the brand (likely Advanced Auto). I was looking for OEM axles either from 6thgen Maxima or Altima but could not find them easily. So I decided to buy these axles in the meantime. Once I get an OEM axle, I will swap back over because I honestly prefer OEM axles on my Maximas.
Initial Review (11/16/2019): At normal cruise speed, not feeling any harsh vibrations or noise. On extreme take-off, I do feel some vibrations. I can live with it for now until I get an OEM one. The vibration is not bad at all because my girlfriend didn’t complain about it lol. I also need to get a wheel alignment.
I have been battling a cylinder 6 misfire (P0306) for many months now. I have spent a lot of time on this website researching, but I can’t seem to find anything that works.
The problem: Intermittent misfiring on cylinder 6 that will come and go. It can switch from misfiring to not misfiring instantly. No change due to driving conditions. It happens on the interstate at 70mph, in neighborhoods at 25mph, and at idle. Some days it runs great, only misfiring for a short time, other days its a battle all day long. Sometimes it accelerates just fine, other times it misfires all the way. The idle is fine. Although it may misfire, the idle stays very normal, with no fluctuation.
I have checked the easy stuff already:
Purchased new OEM coil and installed on cylinder 6
Switched out the new coil from cylinder 6 with a coil from a known good cylinder
Replaced all 6 spark plugs
Switching spark plugs between cylinder 6 and known good cylinder
Switched fuel injectors from cylinder 6 with a known good cylinder
Tugged and pulled on the wiring harness from the front bank of cylinders all the way back to the firewall by the passenger side strut tower
Sprayed starting fluid all around intake plenum, no change in idle
Flashed ECU to an updated version
I have done all of the above, and none have made any difference in the misfiring. Always on cylinder 6.
I, fortunately, know a tech at the local Nissan dealership who also tested the wiring harness and intake plenum with similar results. He also flashed my ECU. He is now saying it’s the ECU because none of the other things have fixed it. His cost on the ECU is $650!
I called David from SpeedometerRepairGuy.com and explained what I needed and he said the ECU rebuild he does for Maxima’s wouldn’t fix my misfiring (only fixes damage from a bad IACV), also stating he had never heard of this problem before. Again, I have no problem with my idle.
Not sure what to try next. A friend of mine suggested the fuel filter, but the Nissan tech was adamant that it couldn’t be the fuel filter, also citing its a “lifetime” part. Thought about just changing it, since it’s so cheap anyway.
Any other ideas of things I should try before getting a new (or used) ECU? I have already purchased one used ECU through car-parts.com and it was bad, so I am 1) trying to avoid the hassle of trying to find a good used ECU and 2) trying to avoid spending $650+ on a new ECU from Nissan. After all, at this point, I don’t know it’s a bad ECU, it’s by deduction that I/we think its the ECU.
I replaced the ECU with a reman unit from the dealership and had them install and reconfigure everything. (I did this as I pulled my then current ECU out and it was clear that water had gotten into the unit and there was corrosion on the board plus my buddy the Nissan tech is usually spot on.) Didn’t misfire for a day, but its back with vengeance now.
Since the posts above, I replaced the spark plugs again with OEMs (had Auotlites before), and today I switched coils between the bad 6th cylinder and a good cylinder (2), and it still continues to misfire and throw a P0306.
I just don’t understand why it would not misfire for 2 straight weeks when I replaced the fuel filter/strainer and then come back. Could it have something to do with fuel pressure? I mean, replacing the fuel filter/strainer does mess with the fuel pressure since you have to disconnect the lines and pull the fuse? I may be wrong, I am no mechanic…
What’s next? Switch out the injector again? I am second-guessing everything I have done now…
The Fix
To follow up on this thread, I checked the compression (dry) and it was 125 across the board. Low, but not inconsistent which is good. Despite the Nissan tech’s advice to not replace the fuel filter (strainer) since it’s a “lifetime” part, I did anyway because it was a $13 part, easy to do, and $13 isn’t a lot to take a chance on in case it does work. I did both the compression test and fuel filter last Thursday (8/19/10) and it hasn’t misfired since. Unbelievable.
It started doing it on Friday 9/3/10. It went 2 weeks without misfiring, and started back again. The frequency seems to be less, however, it is throwing the P0306 code again (same cylinder as before). Since the problem started however long ago, it hasn’t gone that long without misfiring. It leads me to believe that its fuel-related somehow.
A friend suggested that it may be caused by a dirty fuel tank… reasoning that it ran fine for 2 weeks with a brand new fuel filter until it reached the dirty stuff in the tank. It did start misfiring just after I had filled up at the gas station (waiting in line for the car wash at the same station, actually). I just find it hard to believe that a dirty tank could do that and cause the exact same cylinder to misfire, but stranger things have happened.
Well, I got it figured out. There is something loose or a bad connection with the actual connector on the wiring harness which connects to the coil pack. Me and a friend of mine just starting wiggling all of the wires we could find after determining that it had to be something electrical related. By moving the connector itself a hair this or that way, I could cause it to misfire and then stop. We rigged it up to hold its place where it’s not misfiring:
So far so good. It has misfired maybe once or twice in the last week but it was literally just ones or twice and then it would be fine.My mechanic buddy at the Nissan dealership is going to replace it when he can find a spare. I know what you are thinking… Shouldn’t I have noticed this a really long time ago? Well, in hindsight, yes of course. But, it was one of those things that I took for granted and looked past. I never considered it could be something like that…
Grabbed a Nissan mirror with LCD from an 09+ Rogue. It was as simple as running wires in a vehicle I already had gutted. At first, I tapped into power upfront from the mirror but that caused too much of a delay with the camera turn on. So I just grabbed it in the back.
Power for the LCD still came from the original harness
Ran the wires to the back. You can see the cut camera power wires
Down into the trunk. Put some Ensolite around the wires to prevent rubbing.
UPDATE: November 11, 2019 – I programmed a new ECU using the below and worked 100%. It took about 5 minutes. Place charge anywhere between $50-$150 to do this procedure. Super simple!
Every 99-03 Maxima uses the same PIN for the NATS. The pin is “5523“. This is the default “master” PIN.
This means that you can use a BlaZt cable to re-initialize the NATS on any Maxima of those years. This is particularly useful for those who have to replace their ECU and don’t feel like going to the dealership and dropping $100 to get the ECU programmed to their key/immo (or those who simply want to add more keys to their car).
Normally, the PIN is provided to you when you buy the car but most people lose it. Well, now you can finally add your own keys to the car and/or re-program a used ECU’s to the car.
For those who don’t know the PIN, the PIN can be decoded using a software called “Nissan SuperCode”. The software requires the serial number from the BCM that the ECU came from. It will then provide the PIN. The only problem is that when you buy an ECU from a junkyard, they usually don’t provide/know the BCM serial number from the car that the ECU came from. Normally, you’d have to go to the dealer so they can decode it, but now that I discovered this “master” PIN, you can do it yourself!
The following cars all use the same “5523” default PIN:
Left work Friday afternoon everything was okay. No signs of previous issues, no codes. Sitting at a stoplight the car started shaking real bad, hit the gas to go and she kept running but very rough. The check engine came on. I went to blinking mode as a kept driving. Pulled into Autozone read P0300. Nothing obviously disconnected. Smell of raw fuel out the tailpipe with blue/white smoke but not too heavy.
Made it home, the problem continued. I would rev fine and run better at 30/40 MPH but was rough. Left it alone until yesterday. It seemed to run better when cold, but not right.
I have ohmed out the injectors, the coils, all read okay. Pulled all plugs, all are dry except #1, which was a little wet, but none are fouled. Did a compression test (not fully warmed up I am sure) All cylinders came out to 210 PSI, except #4 which was 150. repeated and got the same results.
I can smell raw fuel so I know it is not running right. No leaks. When I crack the throttle and release, I can hear a gurgling sound in the vicinity of the throttle body, maybe at the EGR area/cylinder 5. I have heard that for a while. Maybe related, maybe not. I don’t hear any sign of a vacuum leak.
The Fix
Well, it was fuel related. Specifically, a nearly clogged filter. I would have thought it would have just shut down, but it acted just like a dropped valve. Bought gas at a station I don’t normally buy from. Not sure it was a tank of bad gas or just timing, but the filter was the issue. I thought it might be the fuel pump, but it seems to be running perfectly now.
