I just bought a 2002 ZO6 that has 19k miles on it. The other evening on the way home the car went into limp mode. I went home got the trailer and brought the car home. Here are the codes I pulled...

PCM:
P1120 H TP Sensor 1 Circuit
P1220 H TP Sensor 2 Circuit
P1515 H Command vs Actual Throttle position Performance (PCM module)
P1516 H Command vs Actual Throttle position Performance (TAC module)
TCS:
C1278 H TCS Temporarily Inhibited by PCM
IPC:
U1160 H Loss of Communications with LDCM
A0 LDCM:
U1064 H Loss of Communication with BCM
A1 RDCM:
U1064 H Loss of Communication with BCM
B0-RFA:
U1096 H Loss of Communication with IPC


I cleared the errors and drove down the street. About a quarter mile into the trip and the same thing happened with the following errors:

PCM:
P1515 H Command vs Actual Throttle position Performance (PCM module)
TCS:
C1278 H TCS Temporarily Inhibited by PCM
IPC:
U1160 H Loss of Communications with LDCM
A0 LDCM:
U1064 H Loss of Communication with BCM
A1 RDCM:
U1064 H Loss of Communication with BCM
B0-RFA:
U1096 H Loss of Communication with IPC

This seems like a very random sampling of errors. Almost like I have something loose in the harness. Any ideas?
Thanks
Scott

 

PCM:
P1515 H Command vs Actual Throttle position Performance (PCM module)

This is the only one to put you into limp mode. It is causing the TCS to drop out. The door control module codes are pretty common and can be a non issue or can be a real issue as they share a common bus to the EBCM.

Check the plug connector at the throttle body. Unplug it and inspect it for corrosion and reconnect it. The computer is comparing the throttle/accelerator position sensor reading with the throttle body position sensor reading. If they differ to much, it goes limp.

 

With all of those codes, I'd check the wires in the door accordians 1st.

 

Just removed the TPS sensor connector, looks perfect. Checked the grounds at the ground plug just behind the drivers side head light.

Drove the car and same thing happened. This time only two codes.
P1515 H Command vs Actual Throttle position Performance (PCM module)
C1278 H TCS Temporarily Inhibited by PCM

Most definitely seems like the TPS starting the issue. While under the hood I noticed the large rubber air tube that connects the throttle body to the air intake was loose. Loose enough that air was coming in after the MAF. I wonder if it is possible that something has gotten caught in the throttle body keeping the butterfly valve from working properly.

When the motor is not running, does the valve open if I put my foot down on the accelerator?

(I should have gone over the car with a fine tooth comb)

 

The car TB is connected electrically to your foot, car not on-no movement!

 

So,,, is it fixed?

BC

 

Im waiting to hear to, I have the same code and am basically where your at right now.

Keep us updated!!

Good luck for sure

 

Not fixed yet... I think I may replace the TPS sensor. I have one more thing I am going to try. Although the connections look good, there is a severe kink in the wire as it heads into the connector. I am going to have some one run the car in neutral and I am going to move the wire and see if it is broken under the jacket. But if the TPS sensor is cheap enough I will pick one up on the way home.

Seems so unlikely the sensor would go bad in such a low mileage car. Unfortunately I don't have my service manuals in yet.

I am still wondering if it is possible for a dirty throttle body to behave this way.

 

The TPS should be easy to check with a multimeter. It's just a double potentiometer.
One circuit is:
Dark Green to Purple with Dark Blue for the wiper. You should read a resistance between dark green and purple that does not change when you move the sensor. Between Dark Blue and either of the other wires you should read a resistance that increases when you move the sensor in one direction, decreases when you move it in the other direction.

The second circuit functions the same and the wire colours as follows:
Yellow/black to White with pink as the wiper.

PM an email address and I can send you the schematic.

 

PM sent...

I just got off work so I have had little time to do anything about the car except worry over it.

I called the dealership and they said a TPS sensor was 140 clams. I figure I will determine if it is broke first. I will take the unit off the car and take it to work tomorrow and check the pots.

I do have a friend that has a GM Tech II scan tool. If I can get of work at a reasonable hour I will grab his scan tool and see if I can watch for the failure and look at the live readings. He said that he was not certain the tool would work on my car but he would see if we could get it hooked up.

I did have my wife run the throttle on the car while I wiggled the wiring harnesses around looking for a possible lose wire. Nothing failed while doing that.

I think my best bet is to get the scan tool hooked up. I will keep everyone posted. In the mean time any suggestions are welcome. (well almost any )

 

Fill out your profile so that it says what city and state you live in....you might get lucky and find a person with HP Tuners and also some knowledge that could help you troubleshoot in person. My car is going through the same issues at the time and its driving my tuner mad......Im at home enjoying the stress free environment....

 

Is there any chance when you get on it(about redline 2nd gear) your car will get that code and get REP?

I get 1515 when I do that.The real ball buster is when Im cruising or at a light, and I get 1516 which WILL NOT clear and I have to shut it off and wait lol

 

I'll pay closer attention to what gear, but I have had the code thrown while cruising. In my case I always have to pull over and shut the motor off. But I do not need to be near red line.

 

Take a good solid look at the connector on the throttle body for contamination. You might end up opening the pcm area and looking close at the TAC module but lets hope not.

 

I forgot to mention the car has a Nitrous system on it. (soon to be taken out) I will do a search to find out what was tapped to make it work. I will also look to see if the throttle body was ported.

If I am not mistaken there have been some problems with ported throttle bodies.

 

If one of your Nitrous solenoids are stuck open (even partially) you could have issues but I don't think it would cause what your seeing.

If the bottle was closed, the nitrous solenoid even wide open should't be a problem-if it's a wet system, the fuel solenoid sticking would cause it to run too rich.

 

I was more concerned that the wiring would get messed up if they spliced something to read the pedal or TPS.

 

I think most of these systems actually use a microswitch around the gas pedal inside the cabin to sense WOT.

 

Not to belittle you but do you know how to go through the codes and clear them?

If so you wont have to shut off your car, you can just go in there quick reset it and your good lol (for the time being )

 

I have always reset them by turning the key to the on position and then hold the option button down hit the fuel button four times to get to the menu to manually delete them. Can you the same thing while running?
(don't worry I have thick skin)