2003 Chevrolet Tahoe Repair Question
What could be the source of my reduced engine power warning
a) Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing. The wiring for this and the throttle body quite often causes problems.
b) Verify that the starting and charging systems are operating properly. Low system voltage can cause this DTC to set.
c) When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture
The mechanic wants to replace the TAC and TPS and Throttle Body. Is that going to fix anything if the problem is with the wiring? The same connectors would still be used for the new parts I assume. Why would it only present in the morning? (hard to assess I know)
They might or might not and there are many cases whereby replacement of parts did not help. This is more likely to be an electrical problem and I would suggest checking the wirings first.
It can only occur in the morning because of temperature difference, charging system problem or electrical conductivity and any wrong voltage would cause the code.
If you have a scan tool to monitor the TPS and TAC wiring circuit voltages, that would help identify the problem.
If your mechanicswants to replace the parts, would they take them back if it does not work?
I guess I need to ask him. When I dropped it off I assumed he was going to charge me a flat fee to diagnose. Instead when I picked it up he advised me he had about $175 in it, and the problem still isn't fixed. I don't really want to have him keep "trying" things while I am paying for it by the hour. He replaced the one modulator with a junk yard part, and it didn't fix it, so I am wondering if I should have him put the old one back in. I really don't know how to diagnose the wiring problem. He said when he has it hooked up to the scan tool, and he duplicates the error message, there are no discrepancies in the wiring.
If he is not sure and keeps changing components, he should take them back when replaced components do not solve the problem. Junk yards do accept parts return.
For the wiring problem check all connectors for cleanliness and secure contacts when connected. Ten year old wirings sometimes have increased resistance when terminal crimps deteriorate and these can cause problems as control modules are rather sensitive to minor voltage changes.
I just talked to the mechanic and expressed my concern over the wiring harness. He said that the new ground he put in coming off the TAC would mitigate any circuit issue caused by the wiring harness. He is still insisting that the TB and Accelerator Pedal Positioning Sensor should be changed together.
He is the one doing the job so I can't argue with that as I am not sure of his findings.
Can you answer one more question? Where is the APP Sensor on the 03 Tahoe 5.3L Z-Flex with adjustable pedals? There is a wiring harness and sensor to the left of the brake pedal on the firewall, but I don't see anything attached to the gas pedal that looks like a sensor. I can't find a diagram, as the Haynes manual just gives a written description. Thanks for your time. I can add a photo if that would help.
Thanks, much appreciated. One part, or can you replace just the sensor?