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P0642



DTC P0641, P0642, P0643, P0651, P0652, P0653, P0697, P0698 or P0699

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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-Volt Reference 1 Circuit

DTC P0642
- 5-Volt Reference 1 Low Voltage

DTC P0643
- 5-Volt Reference 1 High Voltage

DTC P0651
- 5-Volt Reference 2 Circuit

DTC P0652
- 5-Volt Reference 2 Low Voltage

DTC P0653
- 5-Volt Reference 2 High Voltage

DTC P0697
- 5-Volt Reference 3 Circuit

DTC P0698
- 5-Volt Reference 3 Low Voltage

DTC P0699
- 5-Volt Reference 3 High Voltage

Diagnostic Fault Information






Circuit/System Description

The engine control module (ECM) has 3 internal 5-volt reference busses called 5-volt reference 1, 5-volt reference 2, and 5-volt reference 3. Each reference bus provides 5-volt reference circuits for more than one sensor. Therefore, a fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to that reference bus. The ECM monitors the voltage on the 5-volt reference busses.

The 5-volt reference 1 bus provides 5 volts to the following sensors:

* The manifold absolute pressure (MAP) sensor
* The clutch apply sensor
* The fuel rail sensor
* The fuel tank pressure (FTP) sensor
* The intake air pressure and temperature sensor

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

* The APP sensor 1
* The exhaust camshaft position (CMP) sensor
* The intake camshaft position (CMP) sensor

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

* The accelerator pedal position (APP) sensor 2
* The crankshaft position (CKP) sensor
* The air conditioning (A/C) refrigerant pressure sensor
* The throttle position (TP) sensor 1 and 2
* The brake booster vacuum sensor

Conditions for Running the DTC

* DTCs P0601, P0602, P0603, P0604, and P0606 are not set.
* The ignition is in Run, or Crank.
* The ignition voltage is more than 5.23 volts.
* DTCs P0641, P0642, P0643, P0651, P0652, P0653, P0697, P0698, and P0699 run continuously when the above conditions are met.

Conditions for Setting the DTC

* DTCs P0641, P0651, and P0697 set when the ECM detects a voltage out of tolerance condition on the 5-volt reference 1, 2 or 3 bus for more than 3 seconds.
* DTCs P0642, P0652, and P0698 set when the ECM detects a low voltage condition on the 5-volt reference 1, 2, or 3 bus for more than 3 seconds.
* DTCs P0643, P0653, and P0699 set when the ECM detects a high voltage condition on the 5-volt reference 1, 2, or 3 bus for more than 3 seconds.

Action Taken When the DTC Sets

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

Conditions for Clearing the DTC

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

Diagnostic Aids

* It may be possible to locate the fault by disconnecting one component at a time from the 5-volt reference circuit while viewing the 5-Volt Reference circuit parameter on the scan tool. The scan tool parameter would change from Fault to OK when the source of the fault is disconnected.
* If all 5-volt reference components have been disconnected and a Fault is still indicated, the fault may exist in the wiring harness.

Circuit/System Verification

With the ignition ON and the engine OFF, observe the 5-volt Reference 1, 2, and 3 parameters. The scan tool should display 4.3-4.7 volts for a normally operating system.

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.

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

2. Ignition ON, measure 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. If all circuits test normal, replace the control module.

3. Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the voltage. The voltage should not change more than 1 volt.

• If the voltage display increases greater than the specified value when a component is connected, test the signal circuit for a short to voltage. If all circuits test normal, replace the control module.
• If the voltage display decreases more than the specified value when a component is connected, replace the component.

Repair Instructions

* Diagnostic Repair Verification
* Accelerator Pedal Position Sensor Replacement
* Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement
* Diagnostic Trouble Code (DTC) List - Vehicle for ECM replacement, setup, and programming.
* Fuel Tank Pressure Sensor Replacement
* Manifold Absolute Pressure Sensor Replacement
* Throttle Body Assembly Replacement
* Camshaft Position Sensor Replacement - Intake
* Camshaft Position Sensor Replacement - Exhaust
* Crankshaft Position Sensor Replacement
* Intake Air Pressure and Temperature Sensor Replacement

Repair Verification

With the ignition ON and the engine OFF, observe the 5-Volt Reference 1, 2 and 3 parameters. The scan tool should display 4.3-4.7 volts for a normally operating system.
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