The engine control module (ECM) provides a 5-volt reference to the following sensors:
• | The accelerator pedal position sensor |
• | The power take off (PTO) accelerator position sensor |
• | The oil pressure sensor |
• | Boost sensor |
• | The exhaust gas recirculation (EGR) position sensor |
• | The variable nozzle turbo (VNT) position sensor |
• | The fuel rail pressure sensor |
The 5-volt reference circuits are independent of each other outside the ECM, but are bussed together inside the ECM. Therefore, a circuit condition on one sensor 5-volt reference circuit may affect the sensor 5-volt reference 1 circuits. The ECM monitors the voltage on the 5-volt reference 1 circuit. If the ECM detects that the voltage is out of tolerance, this DTC will set.
This diagnostic procedure supports the following DTC:
DTC P0641 5-Volt Reference 1 Circuit
• | The ignition switch is ON. |
• | The battery voltage is between 10-16 volts. |
The 5-volt reference circuit 1 voltage is more than 5.5 volts or less than 4.5 volts.
• | The ECM limits fuel injection quantity for fail-safe operation. |
• | The ECM limits fuel pressure for fail-safe operation. |
• | The ECM closes the EGR valve and holds it in the closed position. |
• | The PTO control is inhibited. |
• | The ECM illuminates the malfunction indicator lamp (MIL) and reduced engine power indicator lamp, if fitted, when the diagnostic runs and fails. |
• | The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records. |
• | The ECM inhibits the cruise control. |
• | The MIL resets when the ignition is turned OFF. |
• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
• | Clear the MIL and the DTC with a scan tool. |
Step | Action | Values | Yes | No | ||||
---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||
2 |
Does the DTC fail this ignition? | -- | Go to Step 3 | Go to Intermittent Conditions | ||||
3 |
Is the voltage within the specified range? | 4.5-5.5 V | Go to Step 7 | Go to Step 4 | ||||
4 |
Was a component replaced? | -- | Go to Step 8 | Go to Step 5 | ||||
5 |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 | ||||
6 |
Important: The replacement engine control module (ECM) must be programmed. Replace the ECM. Refer to Engine Control Module Programming and Setup , Engine Control Module Replacement/Restore Fuel Rate Data , and Fuel Injector Flow Rate Programming . Did you complete the replacement? | -- | Go to Step 8 | -- | ||||
7 | Replace the APP sensor. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- | ||||
8 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 9 | ||||
9 | Observe the stored information, Capture Info with a scan tool. Are there any DTCs that you have not diagnosed? | -- | System OK |