P0642-SENSOR REFERENCE VOLTAGE 1 CIRCUIT LOW

For a complete wiring diagram Refer to Section 8W

When Monitored:
With the ignition on.
Set Condition:
The PCM detects low voltage on the 5 volt supply circuit.

Possible Causes

INTERMITTENT DTC

5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND

ACCELERATOR PEDAL POSITION SENSOR

CAMSHAFT 2 POSITION SENSOR

CRANKSHAFT POSITION SENSOR

THROTTLE POSITION SENSOR

VEHICLE SPEED SENSOR (MTX ONLY)

POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Diagnostic Test

1.DTC IS ACTIVE

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

Is the status Active for this DTC?

Yes

Go to 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2.ACCELERATOR PEDAL POSITION SENSOR

Is the voltage above 4.6 volts?

Yes

Replace the Accelerator Pedal Position Sensor.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 3

3.CAMSHAFT 1/2 POSITION SENSOR

Is the voltage above 4.6 volts?

Yes

Replace the Camshaft 1/2 Position Sensor.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 4

4.CRANKSHAFT POSITION SENSOR

Is the voltage above 4.6 volts?

Yes

Replace the Crankshaft Position Sensor.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 5

5.THROTTLE POSITION SENSOR

Is the voltage above 4.6 volts?

Yes

Replace the Throttle Body in accordance with the Service Information.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 6

6.VEHICLE EQUIPPED WITH MANUAL TRANSMISSION

Is the vehicle equipped with a manual transmission?

Yes

Go to 7

Go to 8

7.VEHICLE SPEED SENSOR

NOTE: Only vehicles equipped with a manual transmission will use a Vehicle Speed Sensor.

Is the voltage above 4.6 volts?

Yes

Replace the Vehicle Speed Sensor.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 8

8.5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND

Is the resistance above 1000 ohms for both circuits?

Yes

Go to 9

Repair the 5 Volt Supply circuit for a short to ground.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

9.POWERTRAIN CONTROL MODULE (PCM)

Were any problems found?

Yes

Repair as necessary.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Replace the PCM in accordance with the Service Information.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE)