For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provide an overview of each diagnostic category.

### DTC Descriptors

DTC P0641: 5-Volt Reference 1 Circuit
DTC P0651: 5-Volt Reference 2 Circuit
DTC P0697: 5-Volt Reference 3 Circuit

### Circuit/System Description

The engine control module (ECM) has 3 5-volt reference circuits. The ECM provides the 5-volt reference to various sensors. Each reference circuit provides a 5-volt reference for greater than one sensor. A short to ground or voltage on one of the 5-volt reference circuits will affect all components connected to that 5-volt reference circuit. The ECM monitors the voltage on the 5-volt reference circuits.

### Conditions for Running the DTC

• | The ignition is ON.

• | The DTCs run continuously when the above condition is met.

### Conditions for Setting the DTC

The control module detects a voltage above a predetermined threshold, on any of the 5-volt reference circuits, for greater than 4 seconds.

### Action Taken When the DTC Sets

DTCs P0641, P0651, and P0697 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0641, P0651, and P0697 are Type B DTCs.

### Diagnostic Aids

• | The 5-volt reference 1 circuit provides 5 volts to the following sensors:

- | The fuel tank pressure (FTP) sensor (if equipped)

- | The engine oil pressure (EOP) sensor

• | The 5-volt reference 2 circuit provides 5 volts to the following sensors:

- | All four camshaft position (CMP) sensors

- | Accelerator pedal position (APP) sensor 1

• | The 5-volt reference 3 circuit provides 5 volts to the following sensors:

- | Throttle position sensor (TPS) 1 and 2

- | Crankshaft position (CKP) sensor

- | Accelerator pedal position (APP) sensor 2

- | A/C pressure sensor

• | If the condition is intermittent, move the related harnesses and connectors with the engine operating. Monitor the scan tool 5-volt Reference Circuit Test Status parameters for the affected components. The circuit test status parameter will change from OK or Not Run to Fault if there is a condition with the circuit or a connection.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the scan tool DTC information. DTCs P0641, P0651, or P0697 should not set.
2. Observe the appropriate scan tool 5-volt Reference Circuit Test Status parameter. The parameter should display OK or Not Run.
3. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

### Circuit/System Testing

Important: Additional DTCs will set when disconnecting the components.

1. Ignition OFF, disconnect the harness connector of all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids.
2. Ignition ON, test for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.

⇒ | If the voltage is less than the specified range, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the control module.

⇒ | If the voltage is greater than the specified range, test for a short to voltage on all the 5-volt reference circuits for each component associated with the appropriate 5-volt reference circuit. If all circuits test normal, replace the control module.

Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.

3. Connect each component associated with the 5-volt reference circuit one at a time while monitoring the scan tool 5 volt reference parameter. The scan tool parameter should not display Fault.

⇒ | If the scan tool displays Fault when a component is connected, test the signal circuit for a short to voltage. If all circuits test normal, replace the component.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement

• | Accelerator Pedal Position Sensor Replacement

• | Crankshaft Position Sensor Replacement

• | Camshaft Position Sensor Replacement - Bank 2 (Left Side) Exhaust

• | Camshaft Position Sensor Replacement - Bank 2 (Left Side) Intake

• | Camshaft Position Sensor Replacement - Bank 1 (Right Side) Exhaust

• | Camshaft Position Sensor Replacement - Bank 1 (Right Side) Intake

• | Engine Oil Pressure Sensor and/or Switch Replacement

• | Throttle Body Assembly Replacement

• | Control Module References for ECM replacement, setup, and programming