Circuit Description
The DTC P0641 5-Volt Reference 1 Circuit diagnostic detects an incorrect voltage on the reference A supply circuit. The powertrain control module (PCM) provides 5 volts to the reference A circuit to the following sensors:
| • | The accelerator pedal position (APP) sensor 1 |
| • | The manifold absolute pressure (MAP) sensor |
| • | The automatic transmission output shaft speed (AT 0SS) sensor |
These 5-volt reference circuits are independent of each other outside the PCM, but are bussed together inside the PCM. Therefore a short circuit condition on the 5-volt reference of one sensor can affect the operation of the other sensors. The PCM monitors the voltage on the 5-volt reference circuit. If the PCM detects that the voltage is out of tolerance, DTC P0641 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0641 5-Volt Reference 1 Circuit
Conditions for Running the DTC
| • | The ignition is ON. |
| • | DTC P0641 runs continuously when the above condition is met. |
Conditions for Setting the DTC
| • | The reference A circuit voltage is less than 4.8 volts or more than 5.2 volts. |
| • | The above condition is present for at least 2 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL). |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after 3 consecutively passing trips without a fault present. |
| • | A history DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Perform the scan tool Clear DTC Information function. |
Diagnostic Aids
Check for any of the following conditions:
A DTC P0641 can set when water shorts the reference circuit high or low. Inspect for water entry into the sensor or PCM electrical connectors.
An intermittent malfunction may be caused by a fault in the 5-volt reference A electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .
If the DTC P0641 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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After replacing the PCM a new minimum throttle position and idle speed must also be established.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
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 Diagnostic Aids |
3 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 9 | Go to Step 4 |
4 | Is the voltage measured in step 3 more than the specified value? | 5.2 V | Go to Step 8 | Go to Step 5 |
5 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 10 | Go to Step 6 |
6 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 11 | Go to Step 7 |
7 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 |
8 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 |
9 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- |
10 | Replace the APP sensor. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- |
11 | Replace the AT OSS sensor. Refer to Output Speed Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- |
Did you complete the replacement? | -- | Go to Step 13 | -- | |
13 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 14 |
14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
