P1628-SENSOR REFERENCE VOLTAGE 2 CIRCUIT ERRATIC





For a complete wiring diagram Refer to Section 8W.



Possible Causes
(F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
(F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO BATTERY VOLTAGE
(F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT OPEN
5-VOLT SENSOR
PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



Diagnostic Test

1. ACTIVE DTC

Ignition on, engine not running.
With a scan tool, select View DTCs.

Is the DTC Active at this time?

Yes


No

2. (F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND



Turn the ignition off.
Disconnect the C1 PCM harness connector.
Disconnect all the Sensors that share the (F856) Auxiliary 5-volt Supply circuit.

NOTE: This code can be caused by the improper installation of after market accessories that may be causing excessive noise on the (F856) 5-volt Supply circuit.


Measure the resistance between ground and the (F856) Auxiliary 5-volt Supply circuit at the CMP Sensor harness connector.

Is the resistance below 100 ohms?

Yes


No

3. SENSOR SHORTED TO GROUND



Connect the C1 PCM harness connector and all the previously disconnected Sensors except for the CMP Sensor harness connector.
Ignition on, engine not running.
Measure the voltage on the (F856) Auxiliary 5-volt Supply circuit in the CMP Sensor harness connector.

NOTE: You must Turn the Ignition OFF when disconnecting any of the Sensor harness connectors and Turn the Ignition On to check the voltage readings.


While monitoring the voltage, disconnect each Sensor harness connector that shares the (F856) Auxiliary 5-volt Supply circuit, one at a time.

Does the voltage increase above 4.5 volts when disconnecting any of the Sensor harness connectors?

Yes


No

4. 5-VOLT SENSOR



Turn the ignition off.
Connect all the previously disconnected Sensors except for the CMP Sensor harness connector.
Ignition on, engine not running.
Measure the voltage on the (F856) Auxiliary 5-volt Supply circuit in the CMP Sensor harness connector.

Is the voltage below 4.5 volts?

Yes


No

5. (F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO BATTERY VOLTAGE



Turn the ignition off.
Disconnect the C1 PCM harness connector.
Disconnect all the Sensors that share the (F856) Auxiliary 5-volt Supply circuit.
Ignition on, engine not running.
Measure the voltage on the (F856) Auxiliary 5-volt Supply circuit at the CMP Sensor harness connector.

Is the voltage above 0 volts?

Yes


No

6. (F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT OPEN



Turn the ignition off.
Reconnect all the sensors that were disconnected in the previous step except the CMP Sensor 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 Miller Special Tool #8815 to perform diagnosis.


Measure the resistance in the (F856) Auxiliary 5-volt Supply circuit from the Sensor harness connector to the appropriate terminal of special tool #8815.
It may be necessary to perform this test from every sensor that uses the (F856) Auxiliary 5-volt Supply circuit.

Is the resistance below 5.0 ohms?

Yes


No

7. 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


No