Hi all! I’m reaching out because I’m stumped and I’m looking for guidance. Any help is appreciated! I recently purchased a 2005 G35 Auto, 82K (shows on the odo). I bought it knowing it was in “limp mode”. The guy I purchased the car from changed the ECM and had most of the dash apart chasing for shorts. He sold it because he believed the transmission TCM is what’s causing the issue.
My intentions with this car are to manual swap it. My donor is a good running (wrecked) 2004 G35 6MT. I’m hesitant to do the swap because I don’t think the problem is with the TCM and I believe I’ll have the exact same issue when the swap is complete. Let me explain:
The car starts and seems to run well. When it’s first started, you can rev the motor up to 2K, and the pedal seems to communicate with the throttle body during the warmup period (although the revs are slow, no matter how much you push on the pedal). After the car warms up and idles normal, or if the RPM drops below 1K, the accelerator pedal shows no throttle control response. Seems like the pedal is dead. There are no ECM codes. I also can’t get the ECM to reset via the pedal dance. I know the procedure, and I have a 2007 G35 that I can pedal dance all day long .
I changed some parts from the 04 to the 05, seeing if any of these part swaps would solve the problem. I changed the pedal assembly, throttle body assembly and IPDM. Each part was changed one at a time and the running condition was tested after the part was replaced. (note: the 2004 is a running and driving car with zero problems with any of these parts). Unfortunately, none of the parts swaps helped.
I then started to examine the connections: Here are my readings for the stuff I tested so far…
Battery Voltage: 14.65 V
ECM terminal no# 47, Sensor Power Supply: KOEO 5.07 V
ECM terminal no# 50, Throttle Positions Sensor 1: KOEO, shift to “D” (released) .71 V
ECM terminal no# 50, Throttle Positions Sensor 1: KOEO, shift to “D” (depressed) 4.1 V
ECM terminal no# 66, Sensor Ground: KOER (warmed up) 37.5 mV
ECM terminal no# 69, Throttle Positions Sensor 2: KOEO, shift to “D” (released) 4.42 V
ECM terminal no# 69, Throttle Positions Sensor 2: KOEO, shift to “D” (depressed) 1.01 V
ECM terminal no# 91, Sensor Power Supply: KOEO 5.07 V
Throttle control actuator terminal #1: 5.06 V
Throttle control actuator terminal #5 and ECM terminal #66: continuity tested good
Throttle control actuator terminal #4 and ECM terminal #50: continuity tested good
ECM terminal no# 82, Sensor Ground: KOER (warmed up) 37 mV
ECM terminal no# 83, Sensor Ground: KOER (warmed up) 36.3 mV
ECM terminal no# 90, Sensor Power Supply APP 1: KOEO 5.07 V
ECM terminal no# 91, Sensor Power Supply APP 2: KOEO 5.07 V
ECM terminal no# 98, APP 2: KOEO, (released) .39 V
ECM terminal no# 98, APP 2: KOEO, (depressed) 2.17 V
ECM terminal no# 106, APP 1: KOEO, (released) .806 V
ECM terminal no# 106, APP 1: KOEO, (depressed) 4.4 V
APP sensor terminal #6: 5.06 V
APP sensor terminal #3 and ECM terminal #82: continuity tested good
APP sensor terminal #5 and ECM terminal #106: continuity tested good
ECM terminal no# 98, APP 2: KOER, warmed up (released) .417 V
ECM terminal no# 98, APP 2: KOER, warmed up (depressed) 2.18 V
ECM terminal no# 106, APP 1: KOER, warmed up (released) .829 V
ECM terminal no# 106, APP 1: KOER, warmed up (depressed) 4.29 V
All these readings show as good when compared to the FSM. What I found interesting is on the next visual test I did.
KOEO, shift lever in “D” – I pulled the intake tube off to visually inspect the butterfly valve. To my surprise, the pedal and TB seems to be working 100% - meaning, if you push the pedal slightly, the butterfly opens slightly. If you push the pedal to WOT, the butterfly valve seems to open all the way. But when KOER, the butterfly valve doesn’t appear to be moving at all. I visually inspected this as I left about a quarter inch opening at the top and had a helper press the accelerator pedal.
What do you think? TCM? Can the TCM limp mode the ECM without ECM codes?
More info, maybe relevant? There were some codes that I pulled from the ABS module and TCM. I cleared them when I started to work on the car. I don’t have a diagnostic scan tool. I use a cheap MaxiLink ML629.
ABS: C1131 (cleared but came back via ML629)
TCM: U1000, P0720 (cleared and never returned to ML629, however, I did the OBD-II self-diagnosis and the A/T CHECK indicator flashes 17 times.)