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: 5 V Reference 1 Circuit
DTC P0642: 5 V Reference 1 Circuit Low Voltage
DTC P0643: 5 V Reference 1 Circuit High Voltage
DTC P0651: 5 V Reference 2 Circuit
DTC P0652: 5 V Reference 2 Circuit Low Voltage
DTC P0653: 5 V Reference 2 Circuit High Voltage
DTC P0697: 5 V Reference 3 Circuit
DTC P0698: 5 V Reference 3 Circuit Low Voltage
DTC P0699: 5 V Reference 3 Circuit High Voltage

### Circuit/System Description

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

### Conditions for Running the DTC

• | The ignition is ON for greater than 3 seconds.

• | DTCs P0641, P0642, P0643, P0651, P0652, P0653, P0697, P0698, and P0699 run continuously when the above condition is met.

### Conditions for Setting the DTC

The 5-volt reference circuit voltage is above or below a predetermined threshold for greater than 1 second or for a cumulative of 10 seconds.

### Action Taken When the DTC Sets

DTCs P0641, P0642, P0643, P0651, P0652, P0653, P0697, P0698, and P0699 are Type A DTCs.

### Conditions for Clearing the DTC

DTCs P0641, P0642, P0643, P0651, P0652, P0653, P0697, P0698, and P0699 are Type A DTCs.

### Diagnostic Aids

#### DTC P0641, P0642, and P0643

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

- | B65 intake air pressure sensor terminal 3

- | B157 secondary air injection (AIR) pressure sensor terminal 1

- | B37 engine oil pressure (EOP) sensor terminal B

- | B25 clutch pedal position (CPP) sensor terminal

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

#### DTC P0651, P0652, and P0653

- | All four B23 camshaft position sensors terminal 3

- | B107 accelerator pedal position (APP) sensor 1 terminal 2

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

#### DTC P0697, P0698, and P0699

- | Q38 throttle position sensor 1 and 2 terminal E

- | B26 crankshaft position sensor terminal 3

- | B107 accelerator pedal position (APP) sensor 2 terminal 1

- | B1 A/C refrigerant pressure sensor terminal 1

• | If the condition is intermittent, move the related harnesses and connectors with the engine operating. Monitor the scan tool 5 V Reference 1, 2, or 3 Circuit Status parameters for the affected components. The 5 V Reference 1, 2, or 3 Circuit 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 DTC information with a scan tool. DTC P0641, P0642, P0643, P0651, P0652, P0653, P0697, P0698, or P0699 should not set.
2. Observe the appropriate scan tool 5 V Reference 1, 2, or 3 Circuit 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 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 of all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids.
2. Ignition ON, test for 4.6-5.2 V between one of the affected 5 V reference circuits and ground.

⇒ | If the voltage is less than the specified range, test for a short to ground or for an open between the ECM and the circuit splice. If the circuit test normal, replace the K20 ECM.

⇒ | If the voltage is greater than the specified range, test for a short to voltage on the 5 V reference circuit. If the circuit 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 affected 5 V reference circuit one at a time while monitoring the appropriate scan tool 5 V Reference 1, 2, or 3 Circuit Status parameter. The parameter should continue to display OK.

⇒ | If the parameter displays Fault when a component is connected, test the signal circuit of that component for a short to voltage. If the circuit tests normal, replace the component.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Turbocharger Pressure Sensor Replacement

• | Clutch Pedal Position Sensor Replacement

• | Secondary Air Injection (AIR) System Pressure Sensor

• | Engine Oil Pressure Sensor Replacement

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

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

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

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

• | Accelerator Pedal Position Sensor Replacement

• | Throttle Body Assembly Replacement

• | Crankshaft Position Sensor Replacement

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

• | Control Module References for engine control module replacement, setup, and programming