• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Air Conditioning (A/C) Refrigerant Pressure Sensor 5-Volt Reference 2 Circuit | P0651 | P0532 | P0651 | -- |
Fuel Tank Pressure (FTP) Sensor 5-Volt Reference 1 Circuit | P0641 | P0452 | P0641 | -- |
Manifold Absolute Pressure (MAP) Sensor 5-Volt Reference 1 Circuit | P0641 | P0107 | P0641 | -- |
Exhaust Gas Recirculation (EGR) Valve 5-Volt Reference 1 Circuit | P0641 | P0404, P0405 | P0406 | -- |
The control module 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 control module 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 exhaust gas recirculation (EGR) valve |
The 5-volt reference 2 bus provides 5 volts to the Air conditioning (A/C) refrigerant pressure sensor
• | DTCs P0601, P0602, P0604, P0606, and P2610 are not set. |
• | The ignition is ON. |
• | The ignition voltage is more than 9.5 volts. |
• | DTCs P0641 and P0651 run continuously when the above conditions are met. |
The control module detects a voltage out of tolerance condition on the 5-volt reference 1 or 2 bus for more than 0.5 second.
• | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
• | Clear the MIL and the DTC with a scan tool. |
Observe the MAP sensor voltage parameter with a scan tool with the ignition ON and the engine OFF. The scan tool should display 3.6-4.8 volts for a normally operating system.
With the ignition ON and the engine OFF, observe the A/C Refrigerant Pressure-A/C High Side Pressure parameter with a scan tool. The scan tool should display 0.2-4.9 volts or 9-453 psi for a normally operating system.
⇒ | If within 4.8-5.2 volts, refer to Testing for Intermittent Conditions and Poor Connections. |
⇒ | If within 4.8-5.2 volts, replace the EGR valve. |
⇒ | If over 5.2 volts, check for unexpected voltage at each 5-volt reference circuit or the signal circuit for each component associated with the 5-volt reference. |
⇒ | If under 4.8 volts, check for a short to ground or low reference circuit at each 5-volt reference circuit. |
⇒ | If the data parameters change with any component being disconnected, replace the component. |
⇒ | If within 4.8-5.2 volts, refer to Testing for Intermittent Conditions and Poor Connections. |
⇒ | If over 5.2 volts, test all 5-volt references circuits for a short to voltage. If all circuits tested are OK, replace the A/C pressure sensor. |
⇒ | If under 4.8 volts, turn OFF the ignition and test all 5-volt references circuits for a short to ground or any sensor low reference circuit. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for engine control module (ECM) replacement, setup, and programming |