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-Volt Reference 1 CircuitDTC 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 | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Accelerator Pedal Position (APP) Sensor 1 5-Volt Reference 2 Circuit | P0652 | P2122 | P0653 | -- |
Accelerator Pedal Position (APP) Sensor 2 5-Volt Reference 3 Circuit | P0698 | P2127 | P0699 | -- |
Air Conditioning (A/C) Refrigerant Pressure Sensor 5-Volt Reference 3 Circuit | P0698 | P0532 | P0699 | -- |
Brake Booster Vacuum Sensor 5-Volt Reference 3 Circuit | P0698 | P0557 | P0699 | -- |
Crankshaft Position Sensor 5-Volt Reference 3 Circuit | P0698 | P0335 | P0699 | -- |
Engine Oil Pressure Sensor 5-Volt Reference 3 Circuit | P0698 | P0520 | P0699 | -- |
Exhaust Camshaft Position Sensor 1 5-Volt Reference 2 Circuit | P0652 | P0365 | P0653 | -- |
Fuel Rail Pressure Sensor 5-Volt Reference 1 Circuit | P0642 | P0192 | P0643 | -- |
Fuel Tank Pressure (FTP) Sensor 5-Volt Reference 1 Circuit | P0642 | P0452 | P0643 | -- |
Intake Camshaft Position Sensor 1 5-Volt Reference 2 Circuit | P0652 | P0340 | P0653 | -- |
Manifold Absolute Pressure (MAP) Sensor 5-Volt Reference 1 Circuit | P0642 | P0107 | P0643 | -- |
Throttle Position (TP) Sensor 1 5-Volt Reference 3 Circuit | P0698 | P0122 | P0699 | -- |
Throttle Position (TP) Sensor 2 5-Volt Reference 3 Circuit | P0698 | P0222 | P0699 | -- |
Intake Air Pressure and Temperature Sensor 5-Volt Reference 1 Circuit | P0642 | P0238 | P0643 | -- |
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
P0641, P0651, and P0697
These DTCs 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.
P0642, P0652, and P0698
These DTCs set when the ECM detects a low voltage condition on the 5-volt reference 1, 2, or 3 bus for more than 3 seconds.
P0643, P0653, and P0699
These DTCs 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. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
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 OK for a normally operating system.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector of all appropriate sensors for the applicable DTC.
- Ignition ON, measure for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
- 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.
Important: Additional DTCs will set when disconnecting the components.
Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.
| ⇒ | 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. |
| ⇒ | 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 Trouble Code (DTC) List - Vehicle for ECM replacement, setup, and programming. |
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.
