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Diagnostic Test

WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
  1. 1)  ACTIVE DTC 

    Ignition on, engine not running.

    With a scan tool, read DTCs.

    Is the DTC active at this time. 

    Yes 

    1. Go To step  2).

    No 

    1. Refer to INTERMITTENT CONDITION .
    2. Perform POWERTRAIN VERIFICATION TEST .
  2. 2)  (F856) 5-VOLT SUPPLY CIRCUIT 
    Fig 1: Checking Manifold Absolute Pressure Sensor 5-Volt Supply Circuit
    GC0002651Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the MAP Sensor harness connector.

    Ignition on, engine not running.

    Measure the voltage on the (F856) 5-volt Supply circuit in the MAP Sensor harness connector.

    Is the voltage between 4.5 to 5.2 volts? 

    Yes 

    1. Go To step  3).

    No 

    1. Go To step  7).
  3. 3)  MAP SENSOR 

    With a scan tool, monitor the MAP Sensor voltage with the Sensor harness connector disconnected.

    Is the voltage above 2.2 volts? 

    Yes 

    1. Replace the MAP Sensor.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  4).
  4. 4)  (K1) MAP SIGNAL CIRCUIT OPEN 
    Fig 2: Checking Manifold Absolute Pressure Sensor Signal Circuit
    GC0002638Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the C2 PCM harness connector.

    CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

    Measure the resistance of the (K1) MAP Signal circuit from the MAP Sensor harness connector to the appropriate terminal of special tool #8815.

    Is the resistance below 5.0 ohms? 

    Yes 

    1. Go To step  5).

    No 

    1. Repair the open in the (K1) MAP Signal circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .
  5. 5)  (K1) MAP SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT 
    Fig 3: Checking Manifold Absolute Pressure Sensor Signal Circuit & Ground Circuit
    GC0002652Courtesy of DAIMLERCHRYSLER CORP.

    Measure the resistance between the (K900) Sensor ground circuit and the (K1) MAP Signal circuit in the MAP Sensor harness connector.

    Is the resistance below 5.0 ohms? 

    Yes 

    1. Repair the short between the (K900) Sensor ground circuit and the (K1) MAP Signal circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  6).
  6. 6)  (K1) MAP SIGNAL CIRCUIT SHORTED TO GROUND 
    Fig 4: Checking Manifold Absolute Pressure Sensor Signal Circuit
    GC0002639Courtesy of DAIMLERCHRYSLER CORP.

    Measure the resistance between ground and the (K1) MAP Signal circuit in the MAP Sensor harness connector.

    Is the resistance below 100 ohms? 

    Yes 

    1. Repair the short to ground in the (K1) MAP Signal circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  10).
  7. 7)  (F856) 5-VOLT SUPPLY CIRCUIT SHORTED TO BATTERY VOLTAGE 
    Fig 5: Checking Manifold Absolute Pressure Sensor 5-Volt Supply Circuit
    GC0002651Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the C1 PCM harness connector.

    Ignition on, engine not running.

    Measure the voltage on the (F856) 5-volt Supply circuit in the MAP Sensor harness connector.

    Is the voltage above 5.2 volts? 

    Yes 

    1. Repair the short to battery voltage in the (F856) 5-volt Supply circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  8).
  8. 8)  (F856) 5-VOLT SUPPLY CIRCUIT OPEN 
    Fig 6: Checking Manifold Absolute Pressure Sensor 5-Volt Supply Circuit
    GC0002635Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

    Measure the resistance of the (F856) 5-volt Supply circuit from the MAP Sensor harness connector to the appropriate terminal of special tool #8815.

    Is the resistance below 5.0 ohms? 

    Yes 

    1. Go To step  9).

    No 

    1. Repair the open in the (F856) 5-volt Supply circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .
  9. 9)  (F856) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND 
    Fig 7: Checking Manifold Absolute Pressure Sensor 5-Volt Supply Circuit
    GC0002636Courtesy of DAIMLERCHRYSLER CORP.

    Measure the resistance between ground and the (F856) 5-volt Supply circuit in the MAP Sensor harness connector.

    Is the resistance below 100 ohms? 

    Yes 

    1. Repair the short to ground in the (F856) 5-volt Supply circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  10).
  10. 10)  PCM 
    NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

    Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

    Were there any problems found? 

    Yes 

    1. Repair as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Replace and program the Powertrain Control Module per Service Information.
    2. Perform POWERTRAIN VERIFICATION TEST .
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