Diagnostic Aids

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
- A bent terminal
- A backed-out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation
When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
You may have to drive the vehicle in order to experience a condition.

Step	Action	Value	Yes	No
Schematic Reference: Automatic Transmission Controls Schematics
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Install the scan tool. Turn ON the ignition, with the engine OFF. IMPORTANT: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Using the scan tool, measure ignition voltage. Is voltage within the specified value?	9-18 V	Go to Step 3	Go to DTC P0562 for low voltage or DTC P0563 for high voltage
3	Turn the ignition OFF. Disconnect the 80-way connector at the TCM. Install the J 39700 breakout box, the J-47275 breakout box adapter and the J 47275-1 magnetic overlay. Do not reconnect the TCM. Additional DTCs may set. Turn ON the ignition, with the engine OFF. Using the DMM, measure the voltage at terminal 71 and ground. Is the voltage greater than the specified value?	6 V	Go to Step 4	Go to Step 8
4	Turn the ignition OFF. Disconnect the AT inline 20-way connector. Turn ON the ignition, with the engine OFF. Additional DTCs may set. Using the DMM, measure voltage on the engine side of the AT inline 20-way connector terminal N and ground. Is the voltage greater than the specified value?	6 V	Go to Step 6	Go to Step 5
5	Connect the AT inline 20-way connector. Remove the transmission oil pan. Refer to Oil Pan Replacement . Remove the connectors to the PCS2 and the SS1, SS2 and SS3. Using the DMM, measure the voltage at each of the solenoid connectors. Is the voltage greater than the specified value?	6 V	Go to Step 7	Go to Diagnostic Aids
6	Test the HSD2 circuit between the TCM and AT inline 20-way connector for a short to voltage. Refer to Testing for a Short to Voltage . Did you find and correct the condition?	-	Go to Step 10	-
7	Replace the AT internal wiring harness. Refer to Wiring Harness Replacement . Did you complete the replacement?	-	Go to Step 10	-
8	IMPORTANT: In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM. Replace the TCM. Refer to Control Module References for replacement, setup and programming.Did you complete the replacement?	-	Go to Step 10	-
9	Perform the following procedure in order to verify the repair: Clear the DTC. Start the engine. Select Specific DTC. Enter DTC P2671. Has the test run and passed?	-	Go to Step 10	Go to Step 2
10	With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List - Vehicle	System OK