Hi Guys,

I have a 2003 g35 sedan A/T and about a month ago I got this code while normally cruising. The car went into limp mode with SLIP/VDC/SES lights on with no throttle response. Pulled over and turned the car off for about 10 secs. After trying this for a couple of times it started responding normally again, but the SES light was on consistently.

I had the code read and I received the P1128 code which is basically the throttle control motor circuit short. I erased it to see if it would come back on and shortly after, it did but after restarting a few more times, I was able to drive it home without any issues with the code stored.

I did extensive research on this and basically some forums e.g. infinitihelp said that the throttle body is the culprit. So I decided to check the resistance on the TB as per FSM and it was fine. The connector also looked fine on the harness. I still decided to replace the TB with the one from Nissan which they remanufacture at the factory. The car ran fine for about 50km and the code came back so I decided to do the IAVL from the dealership. It ran fine for about 200km and the code came back.

I took it to the mechanic who specializes in Nissan/Infiniti and had the harness/wires checked for continuity/voltage drop etc. It all came back fine and since the TB was already replaced, the fault doesn't lie there and the resistance was in range. I was told that if the code does come back after the harness check, then it could be the ecu that needs replacing. After driving another 200-300km, the code came back while the car was warming up. It seems that it comes back randomly.

I just wanted to get your opinion on the matter to see if anyone may have experienced this. Should I be checking something else? Do ecu's go bad on these cars? After doing a lot of research, there is not much on this topic, especially in G's.

Also wanted to add that after disconnecting/reconnecting the accelerator pedal sensor, it seems to run longer before code comes back, but that might just be a coincidence.

Any help from the forums would be appreciated.

Cheers

 

Maybe worth a try.
I would try cleaning the connectors but since they are likely weather pack (silicone gaskets) be sure the cleaner you use is safe with silicone. Many of the spray electrical cleaners will cause the silicone gaskets to swell immediately on contact. After cleaning I would coat the contacts with dielectric grease.
It could also be a intermittent problem with the connector pins. Maybe you could find a replacement connector pigtail and hard wire it to the cable.

 

Yup. I have opened the connector and cleaned the terminal when it happened. I was told that the connector was loose initially possibly from checking continuity but the mechanic had fixed that. I will try cleaning again and readjust the pins but no sign of corrosion, etc.

Grounds are clean. Wiggle tested the connector and all seems good on that side. It leads me back to the ECU just because its directly connected to it and the TP sensors connections (part of the same terminal) are good and so is the TB. I followed the flowchart to eliminate any other contact points but I haven't checked the J/C 4 in the FSM but if it was faulty, I would have seen the drop. I wish there was a way to test the ECU.

I appreciate the suggestions though.
Will keep you guys posted.
Cheers

 

The point of failure on crimped pins such as the weather pack is usually right at the crimp where strands can break from over crimping or flexing. Pretty hard to find an intermittent break in the connection. Its a long shot but I would try replacing the connector if nothing else works. It could just as easily be a connector issue on the ECU end of the harness.

 

I will look at it again carefully but I checked all the pins last time I opened it. Its pretty easy to replace the two wires that directly run from the TB to ECU because I traced them if there is any corrosion. But the continuity is good, no voltage drop, short to ground/power is fine. Harness is good and I was assured it was but I will keep checking if it happens again.

Used ECU isn't that expensive and so is the programming so it might come to that if it does happen again. Hopefully it won't since it is such an intermittent issue.

I don't also see a lot of G's with this problem so its an isolated issue which makes it harder to resolve.

Will keep posting updates.

Cheers

 

Agreed, they are the worst.

 

ae.
I replaced the tb and the pps. No go. Sometimes the g would be fine but then id lose power. The idle would go up to 1k and regardless of the amount of peddle I gave her she never got past 2 1/2. I did the rip but nothing just a temp fix. Could it be the tcmr?

 

You and your mechanics should not be replacing parts unless you can confirm the fault lies with them. When you replace a part and it does not clear the trouble put the original part back.

What you and your mechanics should be doing is closely following the troubleshooting steps in the EC section of the FSM

https://www.nicoclub.com/FSM/G35/Sedan/2003/ec.pdf

You may very well have an intermittent ground connection.

Telcoman

 

So after replacing everything, throttle body, pedal position sensor, cam sensors, crank sensors, and what the hell knock sensor... I finally just said what the hell and replaced the integrated relay box located on a firewall behind the battery, so come to find out I had serious corrosion and rust issues on the pin connectors in the box itself. Basically plug-and-play so, I plugged the connectors up and the car had no issues. This was done 2 days ago. The car has had slight issues, and I must add that I assumed it was going into limp mode but what I was experiencing and still to a point is not limp mode but more of a dead throttle position motor response. I know now where the problem Lays. I'm going to solder the new connectors that might have serious corrosion and rust. I'm going to attach pictures of the old relay box.

 

Thanks for posting your solution! Welcome to the forum, BTW

 

I had something like that happen to my car twice a few years ago and both times I got it replaced it under warranty; I had to fight with the dealership and have them take my request to corporate, since they were trying to blame me. Make sure that stupid lid is nice and secure it's real easy for water to get in there and destroy everything.

 

I got same problem. One wire of accelerations pedal was damaged, replaced it but now engine works on 3k max in a min. Can move only slowly with slow acceleration. Says throttle posutuon sensor, changed throttle but same code. Mechanichs blame ecu.(ECM- engine control module) .not sure it may be damaged

 

EDIT out all this stuff, you bumped a thread for a completely different DTC code, code P1128 is NOT for the throttle position sensor. What code are you throwing exactly?

Ring out the circuit for continuity to the ECM, it's only two wires so it's easy.

Next test for power at the ECM on the throttle motor contact circuit, you will need to backprobe the ECM while it's plugged in for this one since the ECM is controlling the contact in the IPDM.

If the throttle body circuit rings out, you have power on the ECM throttle power circuit, and you have a KNOWN WORKING THROTTLE BODY (this means tested for function, not just "I bought a new one and it's never been tested to work") then yes the problem is PROBABLY the ECM.

You can check the wiring diagram in the FSM section EC - Engine Controls.

 

ECU sensor. I could tell the difference right away the light went off after about a hundred miles and hasn't come back on that was 3 months ago and about 6,000 miles. Took about 15 minutes to change you can find the part online for around $10 or $15 AutoZone sells it for about $36

 

I'm curious to find out what this ECU sensor is?