GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    â€¢ Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    â€¢ Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    â€¢  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0A40: Drive Motor 1 Position Sensor Performance

Diagnostic Fault Information

Drive Motor Generator 1

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Drive Motor Generator 1 Position Sensor S1

P0C52

P0A3F

P0C53, P0A3F

P1B03, P0A40

Drive Motor Generator 1 Position Sensor S3

P0C52

P0A3F

P0C53, P0A3F

P1B03, P0A40

Drive Motor Generator 1 Position Sensor S2

P0C5C

P0A3F

P0C5D, P0A3F

P1B03, P0A40

Drive Motor Generator 1 Position Sensor S4

P0C5C

P0A3F

P0C5D, P0A3F

P1B03, P0A40

Drive Motor Generator 1 Position Sensor Excitation Positive

P0A3F

P0A3F

P0A3F

P1B03, P0A40

Drive Motor Generator 1 Position Sensor Excitation Negative

P0A3F

P0A3F

P0A3F

P1B03, P0A40


Drive Motor Generator 2

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Drive Motor Generator 2 Position Sensor S1

P0A45, P0C57

P0A45

P0C58, P0A45

P1B04, P0A46

Drive Motor Generator 2 Position Sensor S3

P0A45, P0C57

P0A45

P0C58, P0A45

P1B04, P0A46

Drive Motor Generator 2 Position Sensor S2

P0A45, P0C61

P0A45

P0C62, P0A45

P1B04, P0A46

Drive Motor Generator 2 Position Sensor S4

P0A45, P0C61

P0A45

P0C62, P0A45

P1B04, P0A46

Drive Motor Generator 2 Position Sensor Excitation Positive

P0A45

P0A45

P0A45

P1B04, P0A46

Drive Motor Generator 2 Position Sensor Excitation Negative

P0A45

P0A45

P0A45

P1B04, P0A46

Circuit/System Description

The drive motor generator position sensor is monitored by the motor control module (MCM). The MCM monitors the angular position, speed and direction of the drive motor generator based upon the signals of the resolver-type position sensor. The position sensor, or resolver, contains a drive coil, two driven coils and an irregular shaped metallic rotor. The metallic rotor is mechanically attached to the shaft of the drive motor generator. At ignition ON, the MCM outputs a 7 volt ac, 10 kHz excitation signal to the drive coil. The drive coil excitation signal creates a magnetic field surrounding the two driven coils and the irregular shaped rotor. The MCM then monitors the two driven coil circuits for a return signal. The position of the irregular shaped metallic rotor causes the magnetically-induced return signals of the driven coils to vary in size and shape. A comparison of the two driven coil signals allows the MCM to determine the exact position, speed and direction of the drive motor generator. The position sensor is a non-serviceable part of the drive motor generator.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The MCM detects a degraded motor position sensor signal.

Action Taken When the DTC Sets

    â€¢ DTC P0A40 is a Type A DTC.
    â€¢ The hybrid powertrain control module (HPCM) commands the battery energy control module (BECM) to open the high voltage contactor relays.

Conditions for Clearing the DTC

DTC P0A40 is a Type A DTC.

Diagnostic Aids

    â€¢ The drive motor generator position sensor circuits operate at very low current. Extreme care must be taken when probing terminals and manipulating harnesses.
    â€¢ The sensor circuit loops are twisted pair with each pair covered in a foil shield. The shield circuits outside of the transmission are grounded to a stud on the drive motor generator power inverter module (PIM) assembly.
    â€¢ Ensure the drive motor generator position sensor harness shield circuits are properly grounded prior to testing.

Reference Information

Schematic Reference

Hybrid Controls Schematics

Connector End View Reference

    â€¢  Component Connector End Views
    â€¢  Inline Harness Connector End Views

Electrical Information Reference

    â€¢  Circuit Testing
    â€¢  Connector Repairs
    â€¢  Testing for Intermittent Conditions and Poor Connections
    â€¢  Wiring Repairs

Special Tools

DT-48493 Jumper Harness

Circuit/System Testing

    Note: The drive motor generator position sensor circuits require proper circuit integrity for correct system operation. Just a few ohms of additional circuit resistance may cause position sensor signal degradation.

       â€¢ Always inspect position sensor signal connectors for proper terminal contact.
       â€¢ All diagnostic connections must be made with the approved test probes to prevent the creation of poor terminal contact.
       â€¢ Connectors that contain position sensor signal circuits must always be clean and dry prior to mating. Foreign material or moisture within the connector may cause sensor signal degradation.

  1. Ignition OFF, disconnect PIM X1 connector.
  2. Using the Position Sensor Specification table specifications listed below, test the position sensor resistance at the PIM X1 circuits as indicated. Also test each circuit for a short to ground.
  3. ⇒If any of the circuits are not within specification, continue with testing.
    ⇒If all circuits test normal, inspect for proper terminal contact at PIM X1 connector. If PIM X1 terminal contact tests OK, perform the Intermittent Condition Testing below.
  4. Disconnect the transmission X176 24-way connector.
  5. Connect the DT-48493 to the X176 24-way connector at the transmission.
  6. Using the Position Sensor Specification table specifications listed below, test the position sensor resistance at the transmission X176 circuits as indicated. Also test each circuit for a short to ground.
  7. ⇒If all circuits test normal, continue with testing.
    ⇒If any of the circuits are not within specification, test the internal transmission harness for the condition. If the internal transmission harness tests OK, replace the applicable drive motor generator.
  8. Disconnect DT-48493 from the transmission X176 24-way connector.
  9. Connect the DT-48493 to the transmission X176 24-way connector at the vehicle harness.
  10. Disconnect PIM X1 connector.
  11. Using the PIM to Transmission Terminal Reference table listed below, test the vehicle harness continuity between PIM X1 connector and transmission X176. Also test these circuits for short to ground and to the shield circuit if the shield circuit is not presently grounded to the PIM assembly.
  12. ⇒If any of the circuits are not within the specified range, repair or replace the wiring harness.
    ⇒ If all circuits test normal, inspect transmission connector X176 for proper terminal contact. If transmission connector X176 tests OK, inspect the harness for an intermittent concern.

Intermittent Condition Testing

  1. If possible, determine which of the position sensor circuits have the intermittent condition by reviewing the Diagnostic Fault Information table. For example, DTCs P0C57 and P0C52 only set for a short to ground condition on either the S1 or S3 circuit.
  2. Using the Position Sensor Specification table listed below, monitor the position sensor circuits at PIM X1 connector while manipulating the applicable harness and connectors.
  3. ⇒If any of the circuits are not within specification, repair the harness or terminal as required. If a harness repair is indicated and external harness damage is not evident, the most likely location for internal wire damage is near the harness clamping locations.
  4. Disconnect transmission X176 connector and inspect for the following:
  5. • Proper terminal contact
    • Proper terminal retention in the connector
    • Foreign material or moisture
    ⇒Repair, replace or clean the connector as appropriate.
  6. Reconnect all connectors and test drive the vehicle.
  7. ⇒If the DTC sets, replace the applicable drive motor generator and retest for DTCs. If the DTC sets, replace the PIM.

Position Sensor Specification

When Testing at PIM X1 56-way Connector/Terminal

When Testing at Transmission X176 24-way Connector/Terminal

Minimum Resistance

Maximum Resistance

Use the DT-48493 to test at X176

55-56

8-9

7.0 ohms

9.0 ohms

53-54

10-11

23 ohms

26 ohms

51-52

12-14

20 ohms

23 ohms

52-56

8-12

Over 1 M ohm

--

54-56

8-10

Over 1 M ohm

--

52-54

10-12

Over 1 M ohm

--


PIM to Transmission Terminal Reference

PIM Connector X1 56-Way Connector/Terminal

Transmission X176 24-Way /Terminal

Minimum Resistance

Maximum Resistance

Harness Continuity Test

56

8

--

less than 1 ohm

55

9

--

less than 1 ohm

54

10

--

less than 1 ohm

53

11

--

less than 1 ohm

52

12

--

less than 1 ohm

51

14

--

less than 1 ohm

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    â€¢  Control Module References for PIM replacement, setup and programming.
    â€¢  Drive Motor with Generator Assembly Removal - 1st Position.
    â€¢  Transmission Control Wiring Harness Extension Harness Removal.