P1628-SENSOR REFERENCE VOLTAGE 2 CIRCUIT ERRATIC

For a complete wiring diagram, refer to the Wiring Information.

When Monitored:
Ignition on.
Set Condition:
When the Powertrain Control Module (PCM) recognizes the Auxiliary 5-Volt Supply circuit voltage is varying too much to quickly. One Trip Fault. ETC light is flashing.

Possible Causes
(K856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
(K856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE
(K856) AUXILIARY 5-VOLT SUPPLY CIRCUIT OPEN
5-VOLT SENSOR
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 DIAGNOSTIC TROUBLE CODE (DTC)

NOTE: Improperly installed aftermarket accessories can cause this DTC to set. Check for any improperly installed aftermarket accessories before continuing with this test.

1.	Start the engine and allow it to idle for at least 60 seconds.

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 may result in possible serious or fatal injury.

2.	With a scan tool, read the active DTCs.

Is the DTC Active at this time?

Yes

Go To 2

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

2. (K856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND

1.	Turn the ignition off.

2.	Disconnect the PCM C2 harness connector.

3.	Disconnect all the Sensors that share the (K856) Auxiliary 5-Volt Supply circuit.

4.	Disconnect the APP Sensor harness conector.

NOTE: This code can be caused by the improper installation of after market accessories that may be causing excessive noise on the (K856) 5-Volt Supply circuit.

5.	Measure the resistance between ground and the (K856) Auxiliary 5-Volt Supply circuit at the CMP 1/1 Sensor harness connector.

Is the resistance below 100 Ohms?

Yes

Repair the short to ground in the (K856) Auxiliary 5-Volt Supply circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 3

3. SENSOR SHORTED TO GROUND

1.	Connect the PCM C2 harness connector and all the previously disconnected Sensors except for the CMP 1/1 Sensor harness connector.

2.	Ignition on, engine not running.

3.	Measure the voltage on the (K856) Auxiliary 5-Volt Supply circuit in the CMP 1/1 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.

4.	While monitoring the voltage, disconnect each Sensor harness connector that shares the (K856) Auxiliary 5-Volt Supply circuit, one at a time including the APP Sensor harness connector.

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

Yes

Verify that there is good pin to terminal contact in the related Sensor and Powertrain Control Module harness connectors. If OK, replace the Sensor that causes the (K856) Auxiliary 5-Volt Supply circuit voltage to increase when disconnected.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 4

4. 5-VOLT SENSOR

1.	Turn the ignition off.

2.	Connect all the previously disconnected Sensors except for the CMP 1/1 Sensor harness connector.

3.	Ignition on, engine not running.

4.	Measure the voltage on the (K856) Auxiliary 5-Volt Supply circuit in the CMP 1/1 Sensor harness connector.

Is the voltage below 4.5 Volts?

Yes

Go To 5

Verify that there is good pin to terminal contact in the CMP Sensor and Powertrain Control Module connectors. If OK, replace the Camshaft Position Sensor. (Refer to 08 - Electrical/8I - Ignition Control/SENSOR, Camshaft Position - Removal) .
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

5. (K856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE

1.	Turn the ignition off.

2.	Disconnect the PCM C2 harness connector.

3.	Disconnect all the Sensors that share the (K856) Auxiliary 5-Volt Supply circuit.

4.	Disconnect the APP Sensor harness connector.

5.	Ignition on, engine not running.

6.	Measure the voltage on the (K856) Auxiliary 5-Volt Supply circuit at the CMP 1/1 Sensor harness connector.

Is there any voltage present?

Yes

Repair the short to voltage in the (K856) Auxiliary 5-Volt Supply circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 6

6. (K856) AUXILIARY 5-VOLT SUPPLY CIRCUIT OPEN

1.	Turn the ignition off.

2.	Reconnect all the sensors that were disconnected in the previous step except the CMP 1/1 Sensor harness connector.

3.	Measure the resistance in the (K856) Auxiliary 5-Volt Supply circuit from the Sensor harness connector to the PCM C2 harness connector.

4.	It may be necessary to perform this test from every sensor that uses the (K856) Auxiliary 5-Volt Supply circuit.

Is the resistance below 5.0 Ohms?

Yes

Go To 7

Repair the open in the (K856) Auxiliary 5-Volt Supply circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

7. POWERTRAIN CONTROL MODULE (PCM)

1.	Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the related Sensors 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 related Sensor and Powertrain Control Module connectors.

4.	Perform 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).

Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. (Refer to 08 - Electrical/8E - Electronic Control Modules/MODULE, Powertrain Control - Removal) .
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

P1628-SENSOR REFERENCE VOLTAGE 2 CIRCUIT ERRATIC

P1628-SENSOR REFERENCE VOLTAGE 2 CIRCUIT ERRATIC

Possible Causes