Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic Test
- ACTIVE DTC
- Start the engine and allow it to reach normal operating temperature.WARNING:
When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.
- With the scan tool, select View DTCs.
Is the status Active for this DTC?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
- Start the engine and allow it to reach normal operating temperature.
- CHECK THE (F856) 5-VOLT SUPPLY CIRCUIT FOR A SHORT TO VOLTAGE
- Turn the ignition off.
- Disconnect the MAP Sensor harness connector.
- Turn the ignition on.
- Measure the voltage of the (F856) 5-Volt Supply circuit at the MAP Sensor harness connector.
Does the voltage measure above 5.0 volts?
Yes
- Go To 3
No
- Repair the (F856) 5-Volt Supply circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
- CHECK THE (K1) MAP SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
- Measure the voltage of the (K1) MAP Sensor Signal circuit at the MAP Sensor harness connector.
Does the voltage measure above 5.0 volts?
Yes
- Repair the (K1) MAP Sensor Signal circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
No
- Go To 4
- Measure the voltage of the (K1) MAP Sensor Signal circuit at the MAP Sensor harness connector.
- CHECK THE (K1) MAP SIGNAL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
- Turn the ignition off.
- Disconnect the PCM C2 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 the GPEC Diagnostic Adaptor to perform the diagnosis.
- Connect the (special tool #10436, Adapter, GPEC Diagnostic).
- Measure the resistance of the (K1) MAP Sensor Signal between the MAP Sensor harness connector and the GPEC Adaptor.
Is the resistance below 5.0 Ohms?
Yes
- Go To 5
No
- Repair the (K1) MAP Sensor Signal for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
- CHECK THE (K900) SENSOR GROUND CIRCUIT FOR AN OPEN/HIGH RESISTANCE
- Measure the resistance of the (K900) Sensor Ground circuit between the MAP Sensor harness connector and the GPEC Adaptor.
Is the resistance below 5.0 Ohms?
Yes
- Go To 6
No
- Repair the (K900) Sensor Ground circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
- Measure the resistance of the (K900) Sensor Ground circuit between the MAP Sensor harness connector and the GPEC Adaptor.
- MAP SENSOR
- Turn the ignition off.
- Reconnect the PCM C2 harness connector.
- Connect a jumper between the (K900) Sensor Ground circuit and the (K1) MAP Sensor Signal circuit in the MAP Sensor harness connector.
- Turn the ignition on.
- With the scan tool, read the MAP Sensor signal voltage.
Is the voltage below 0.1 volt with the jumper in place?
Yes
- Replace the MAP Sensor in accordance with the service information. Refer to SENSOR, MANIFOLD AIR PRESSURE (MAP), REMOVAL .
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
No
- Go To 7
- POWERTRAIN CONTROL MODULE (PCM)
- Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Manifold Absolute Pressure Sensor and the Powertrain Control Module (PCM).
- Look for any chafed, pierced, pinched, or partially broken wires.
- Look for broken, bent, pushed out or corroded terminals.
- Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
- Look for the data to change or for the DTC to reset during the wiggle test.
- Perform the Technical Service Bulletins that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
No
- Replace and program the Powertrain Control Module (PCM) in accordance with the service information. Refer to MODULE, POWERTRAIN CONTROL, REMOVAL .
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.