For 1990-2009 cars

### Diagnostic Instructions

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

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

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

### DTC Descriptors

DTC P0641 03: 5V Reference 1 Circuit Below Threshold
DTC P0641 07: 5V Reference 1 Circuit Above Threshold
DTC P0651: 5V Reference 2 Circuit
DTC P0651 03: 5V Reference 2 Circuit Below Threshold
DTC P0651 07: 5V Reference 2 Circuit Above Threshold
DTC P0697 03: 5V Reference 3 Circuit Below Threshold
DTC P0697 07: 5V Reference 3 Circuit Above Threshold

### 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 5.5 volts, or below 4.5 volts, on any of the 5-volt reference circuits for greater than 0.5 second.

### Action Taken When the DTC Sets

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

• | The ECM commands the TAC system to operate in a Reduced Engine Power mode.

### Conditions for Clearing the DTC

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

### Diagnostic Aids

• | If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.

• | The scan tool 5V reference circuit status parameter should display OK.

#### P0641

The 5-volt reference 1 circuit provides 5 volts to the accelerator pedal position (APP) sensor 1

#### P0651, P0652, P0653

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

• | The accelerator pedal position (APP) sensor 2

• | The fuel rail pressure (FRP) sensor

• | The turbocharger boost pressure sensor

#### P0697

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

• | The air conditioning (A/C) refrigerant pressure sensor

• | The water in fuel sensor

• | The diesel particulate filter (DPF) pressure sensor

### 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 DTC information with a scan tool. DTCs P0641, P0651, and P0697 should not set.
2. 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 you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

Note: Additional DTCs will set when disconnecting the components.

1. Ignition OFF, disconnect the harness connector at all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids.
2. Ignition ON, test for 4.6-5.4 V between one of the 5-volt reference circuits and ground.

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

⇒ | If greater than the specified range, test the 5-volt reference circuit for each component associated with the appropriate 5-volt reference circuit for a short to voltage. If all circuits test normal, replace the K20 ECM.

Note: 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 5V reference circuit status 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.

• | Intake Air Pressure and Temperature Sensor Replacement

• | Exhaust Pressure Sensor Replacement

• | Accelerator Pedal Position Sensor Replacement

• | Fuel Injection Fuel Rail Assembly Replacement

• | Water in Fuel Indicator Sensor Replacement

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

### Repair Verification

Ignition ON, observe the scan tool DPF soot mass parameter. The parameter should be less than 10 grams.

⇒ | If greater than the specified range, perform a DPF service regeneration. Refer to Exhaust Particulate Filter Cleaning.