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Cbrowne · 04-09-2024, 11:22 AM

I've done some more investigative work and have a few measured values.

Firstly, each cable from the APP to the ECM is reading 0.2 Ohms, no shorts and no open circuits.

Secondly, the outputs from the APP are as follows:

At 0% throttle - Sensor 1 = 0.958V and Sensor 2 = 0.482V 99.9% accurate
At 100% throttle - Sensor 1 = 3.852V and Sensor 2 = 1.924V 99.9% accurate

However, the ECM is reading:

At 0% throttle - Sensor 1 = 21% and Sensor 2 = 10% 95% accurate
At 100% throttle - Sensor 1 = 79.5% and Sensor 2 = 42.75% 93% accurate

What I believe is happening is as sensor 1 is increasing if it doesn't quite reach the 90% accurate threshold of sensor 2 then it will go into P2138 fault. Next step will be to power up a programmable 5V power supply and look for any voltage drop between the pedal and the ECM plugs.

What I have also found by shorting out the APP is that sensor 1 can only reach a max of 90% whereas sensor 2 goes straight to 100%. In addition to this, sensor 1 doesn't go straight to 90%, it typically reaches 85% before incrementally going to 90%.

It is definitely leaning towards my ECM going bad so will get some quotes through for a clone and looking at swapping them out.

04-09-2024, 11:22 AM	#12
Cbrowne Drives: 2012 LFX Chevrolet Camaro Join Date: Feb 2024 Location: England Posts: 6	Update 3: I've done some more investigative work and have a few measured values. Firstly, each cable from the APP to the ECM is reading 0.2 Ohms, no shorts and no open circuits. Secondly, the outputs from the APP are as follows: At 0% throttle - Sensor 1 = 0.958V and Sensor 2 = 0.482V 99.9% accurate At 100% throttle - Sensor 1 = 3.852V and Sensor 2 = 1.924V 99.9% accurate However, the ECM is reading: At 0% throttle - Sensor 1 = 21% and Sensor 2 = 10% 95% accurate At 100% throttle - Sensor 1 = 79.5% and Sensor 2 = 42.75% 93% accurate What I believe is happening is as sensor 1 is increasing if it doesn't quite reach the 90% accurate threshold of sensor 2 then it will go into P2138 fault. Next step will be to power up a programmable 5V power supply and look for any voltage drop between the pedal and the ECM plugs. What I have also found by shorting out the APP is that sensor 1 can only reach a max of 90% whereas sensor 2 goes straight to 100%. In addition to this, sensor 1 doesn't go straight to 90%, it typically reaches 85% before incrementally going to 90%. It is definitely leaning towards my ECM going bad so will get some quotes through for a clone and looking at swapping them out.