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Do you know anything about ECM five volt reference circuit's ?
DTC P0641: 5-Volt Reference 1 Circuit
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
Possible causes
- Faulty Engine Control Module (ECM)
- ECM harness is open or shorted
- ECM circuit poor electrical connection
- Shorted sensor on 5 volt circuit What does this mean? When is the code detected?
The Engine Control Module (ECM) has detected the sensor 5 volt reference circuit voltage is higher or lower than expected
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
P0641 Chevrolet Description
The control module has 2 internal 5-volt reference buses called "5-volt reference 1" and"5-volt reference 2". Each reference bus provided 5-volt reference circuit 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 the reference bus. The control module monitors the voltage on the 5-volt reference buses.
P0641 Chevrolet Description
The control module has 2 internal 5-volt reference buses called 5-volt reference 1 and 5-volt reference 2 . Each reference bus provided 5-volt reference circuit 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 the reference bus. The control module monitors the voltage on the 5-volt reference buses.
Diagnostic Fault Information Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit/System Description The engine control module (ECM) has 2 internal 5-volt reference busses called 5-volt reference 1 and 5-volt reference 2. 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 fuel tank pressure (FTP) sensor * The air conditioning (A/C) refrigerant pressure sensor * The accelerator pedal position (APP) sensor 2 * The intake camshaft position (CMP) sensor
The 5-volt reference 2 bus provides 5 volts to the following sensors: * The APP sensor 1 * The throttle position (TP) sensor 1 and 2 * The crankshaft position (CKP) sensor
Conditions for Running the DTC * DTCs P0601, P0602, P0603, P0604, P0605, P0606, P0607, and P2610 are not set. * The ignition is in Unlock, Accessory, Run, or Crank. * The ignition voltage is more than 5.23 volts. * DTCs P0641 and P0651 run continuously when the above conditions are met.
Conditions for Setting the DTC The ECM detects a voltage out of tolerance condition on the 5-volt reference 1 or 2 bus for more than 0.5 second.
Action Taken When the DTC Sets DTCs P0641 and P0651 are Type A DTCs.
Conditions for Clearing the MIL/DTC DTCs P0641 and P0651 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 and 2 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 value, 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 value, test for a short to voltage on all the 5-volt reference circuits, or the signal circuit, for each component associated with the appropriate 5-volt reference circuit. 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 changes more than the specified value when a component is connected, replace the component.
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P0652 DODGE - 5 Volt Sensor Reference 2 Circuit Low These 5-volt reference circuits are independent of each other outside
the PCM, but are bussed together inside the Engine Control Module (ECM).
Therefore a circuit condition on one sensor 5-volt reference circuit
may affect the other sensor 5-volt reference circuits. The ECM monitors
the voltage on the 5-volt reference circuit.
What does this mean? When is the code detected?
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