P063A-GENERATOR VOLTAGE SENSE CIRCUIT




For a complete wiring diagram Refer to the Wiring Information.

When Monitored:
The engine running. The engine speed greater than 1157 RPM.

Set Condition:
The PCM recognizes the alternator output voltage is less than the Battery feed circuit voltage. One trip failure. The Generator light will illuminate. The fault will be checked again on the next key cycle.


Possible Causes
EXCESSIVE RESISTANCE IN THE (A803) GENERATOR SENSE CIRCUIT
(A803) GENERATOR SENSE CIRCUIT SHORTED TO GROUND
GENERATOR
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).



1. ACTIVE DTC


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NOTE: Inspect the vehicle for aftermarket accessories that may exceed the Generator System output.

NOTE: The battery must be fully charged.

NOTE: The Generator belt tension and condition must be checked before continuing.
1. Ignition on, engine not running.
2. With a scan tool, select View DTCs.
3. Start the engine.
4. Allow the idle to stabilize.
5. With the scan tool, View DTCs.


Is the DTC Active at this time?

Yes

Go To 2

No

Refer to the INTERMITTENT CONDITION Diagnostic Procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).




2. EXCESSIVE RESISTANCE IN THE (A803) GENERATOR SENSE CIRCUIT


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1. Turn the ignition off.
2. Disconnect the Generator harness connector.
3. Disconnect the C1 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the PCM Pinout Box 8815 to perform diagnosis.


4. Measure the resistance of the (A803) Generator Sense circuit from the Generator harness connector to the appropriate terminal of special tool #8815.


Is the resistance below 5.0 ohms?

Yes

Go To 3

No

Repair the excessive resistance in the (A803) Generator Sense circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).




3. (A803) GENERATOR SENSE CIRCUIT SHORTED TO GROUND


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1. Measure the resistance between ground and the (A803) Generator Sense circuit at the Generator harness connector.


Is the resistance below 100 ohms?

Yes

Repair the short to ground in the (A803) Generator Sense circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

No

Go To 4




4. GENERATOR OPERATION


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1. Connect the C1 PCM harness connector.
2. Using a 12-volt test light connected to ground, probe the (K20) Generator Field Control circuit in the Generator Field harness connector.
3. Ignition on, engine not running.
4. With a scan tool, actuate the Generator Field Driver.


NOTE: The DTC needs to be cleared before actuating the Solenoid, if the DTC is not cleared, the Solenoid may not be allowed to actuate.

NOTE: The test light should be illuminated and bright proportional to the maximum duty cycle allowed by the scan tool. For example, if the scan tool allows 100% actuation, the brightness should be as bright as a direct connection to the battery. If the scan tool allows a maximum 25% actuation, the brightness should be 25% as bright as a direct connection to the battery.


Does the test light illuminate accordingly during the actuation?

Yes

Verify that there is good pin to terminal contact in the Generator and Powertrain Control Module connectors. Replace the Generator if no problems were found with the connectors.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

No

Go To 5




5. POWERTRAIN CONTROL MODULE (PCM)


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1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Generator and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Generator and Powertrain Control Module connectors.
4. Refer to any Technical Service Bulletins that may apply.


Were there any problems found?

Yes

Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

No

Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

 

that is why i said dealer might have to do it because of our scan tool ability.

 

If your going to do a PCM reset try it this way:
The procedure is to pull fuse #23 in box next to battery, hop in the truck, close the doors, put on seat-belt, insert key to the on position, then to the start position (don't crank it).. wait until you hear two chimes (takes about 5 seconds or so before the chimes sound), then key back to off position. Get out, put fuse back in and then
start the truck (don't worry if there is a 2-3 second delay for the truck to start.. that means the PCM was reset). Then your good to go.. of course the resetting means the PCM has to relearn your driving habits.



Good Luck,

Rob