Diagnostic Test
- (A919) PCM FUSED B+ CIRCUIT NOTE: The scan tool and cable must be operating properly for the results of this test to be valid.NOTE: Make sure the ignition switch was on while trying to communicate with the PCM.
Turn the ignition off.
Disconnect the PCM harness connectors.
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 Miller Special Tool #8815 to perform diagnosis.Using a 12-volt test light connected to ground probe the appropriate terminal of special tool #8815.
Does the test light illuminate brightly?
- Yes : Go To 2
- No
: Repair the open or short to ground in the (A919) Fused B+ circuit. Inspect and replace fuses as necessary.
Perform NGC POWERTRAIN VERIFICATION TEST VER - 1 .
- (F202) (F924) PCM FUSED IGNITION SWITCH CIRCUITS
Using a 12-volt test light connected to ground, probe the PCM Fused Ignition Switch Output circuit in the the appropriate terminals of special tool #8815.
Does the test light illuminate brightly?
- Yes : Go To 3
- No : Repair the (F202) (F924) Ignition Switch Output circuit. Inspect and replace fuses as necessary.
- (Z913) (Z937) PCM GROUND CIRCUITS
Using a 12-volt test light connected to battery voltage, probe the (Z913) (Z937) PCM ground circuits in the appropriate terminals of special tool #8815.
Does the test light illuminate brightly?
- Yes : Go To 4
- No : Repair the PCM ground circuits.
- (F855) 5-VOLT SUPPLY CIRCUIT
Turn the ignition off.
Connect the PCM harness connectors.
Disconnect the Crankshaft Position Sensor harness connector.
Ignition on, engine not running.
Measure the voltage on the (F855) 5-volt Supply circuit.
Is the voltage between 4.5 and 5.2 volts?
- Yes : Go To 5
- No : Go To 6.
- CKP SENSOR
Turn the ignition off.
Disconnect the Throttle Body harness connector.
NOTE: Connect the TP Sensor harness connector.Ignition on, engine not running.
Measure the voltage on the (F855) 5-volt Supply circuit in the Throttle Body harness connector.
Is the voltage between 4.5 and 5.2 volts?
- Yes : If communication is available with a PCM on a like vehicle, replace and program the Powertrain Control Module per Service Information.
- No : Replace the Crankshaft Position Sensor.
- (F855) 5-VOLT SENSOR OPEN/SHORTED
Turn the ignition off.
Disconnect the TP Sensor/Throttle Body harness connector.
Ignition on, engine not running.
Measure the voltage on the (F855) 5-volt Supply circuit.
Disconnect all the sensors that use the (F855) 5-volt Supply circuit.
Did the voltage return to 4.5 to 5.2 volts when disconnecting any of the sensors.
- Yes : Replace the sensor that is pulling down the (F855) 5-volt supply.
- No : Go To 7
- (F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect PCM harness connectors.
Disconnect all the sensors that share the (F855) 5-volt Supply circuit.
Measure the resistance between ground and the (F855) 5-volt Supply circuit at one of the sensor harness connectors.
Is the resistance below 100 ohms?
- Yes : Repair the short to ground in the (F855) 5-volt Supply circuit.
- No : Go To 8
- (F856) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
Disconnect all the sensors that share the (F856) 5-volt Supply circuit. Measure the resistance between ground and the (F856) 5-volt Supply circuit at one of the sensor harness connectors.
Is the resistance below 100 ohms?
- Yes : Repair the short to ground in the (F856) 5-volt Supply circuit.
- No : Go To 9
- PCM NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Were there any problems found?
- Yes : Repair as necessary.
- No : Replace and program the Powertrain Control Module per Service Information.