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Wire tap to body ground on APPS wire


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In the C1 connector on my PCM, the orange/black tracer wire that leads to the TPS has a wire tap connected to it leading to body ground. It is tapped a few inches out from the PCM. I am having no issues at this time, just curious if anyone knows what this is all about. It does not appear factory, and wiring diagram does not show that wire going to ground for any reason. 

 

02 automatic. 

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Thanks for the reply. I read through both of the modifications yesterday, and while doing some preliminary investigating noticed the wire tap I mentioned.  What it’s trying to be achieved with the wire tap I described? 

 

Additionally, what is the noise filter on the PCM? And what is the process to check for alternator AC noise? 

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  • Owner
7 hours ago, FosterW said:

What it’s trying to be achieved with the wire tap I described?

 

Attempting to clear the APPS of AC noise. Actually, it can cause issues or damage for the ECM. Sensor ground is NOT body ground.

 

7 hours ago, FosterW said:

Additionally, what is the noise filter on the PCM?

 

A noise filter for filtering out the AC noise getting into the PCM which typically does the 45 MPH hunting of the torque converter. 

 

7 hours ago, FosterW said:

And what is the process to check for alternator AC noise?

 

Measure the AC noise of the BATT terminal and body ground. 50mV AC is marginal 100mV AC is a fail. Like now with all the mods I'm down to as low as like 18mV AC. 

 

 

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  • Owner

Still, in all, there is absolutely no need for this mod adding a ground wire to the APPS sensor leads. 

 

Just remove that ground wire and repair the wire. Now test the alternator for excessive AC noise. If excessive AC noise is found replace the diode pack or replace the alternator. Now you'll want to do the W-T ground wire mod. Then for safety, you want to do my PCM protection mod as an add on. 

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