P0068

P0068-MANIFOLD PRESSURE/THROTTLE POSITION CORRELATION

For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.

The Powertrain Control Module (PCM) performs the following rationality tests which can result in reporting this DTC:

Manifold Pressure Rationality

- When Monitored:
Engine speed is above 550 RPM and has been for more than one second and the total effective throttle area is above a certain threshold (mapped against engine speed).

- Set Condition:
The mass air flow value (g/s) of sensor 1 does not correlate with the estimated mass air flow value for sensor 1 and the mass air flow sensor value (g/s) of sensor 2 does not correlate with the estimated mass air flow value of sensor 2 and the manifold pressure sensor value (kPa) does not correlate with the estimated manifold pressure value and both mass air flow sensors and the effective opening area of both throttles indicate a 50/50 split. One Trip Fault. Three good trips to turn off the MIL.

Mass Air Flow 1 Rationality

- When Monitored:
Engine speed is above 550 RPM and has been for more than one second and the total effective throttle area is above a certain threshold (mapped against engine speed).

- Set Condition:
The mass air flow value (g/s) of sensor 1 does not correlate with the estimated mass air flow value for sensor 1 and the mass air flow value (g/s) of sensor 2 does correlate with the estimated mass air flow value of sensor 2 and the manifold pressure sensor value (kPa) does not correlate with the estimated manifold pressure value. One Trip Fault. Three good trips to turn off the MIL.

Mass Air Flow 2 Rationality

- When Monitored:
Engine speed is above 550 RPM and has been for more than one second and the total effective throttle area is above a certain threshold (mapped against engine speed).

- Set Condition:
The mass air flow value (g/s) of sensor 1 does not correlate with the estimated mass air flow value for sensor 1 and the mass air flow value (g/s) of sensor 2 does correlate with the estimated mass air flow value of sensor 2 and the manifold pressure sensor value (kPa) does not correlate with the estimated manifold pressure value. One Trip Fault. Three good trips to turn off the MIL.

Manifold Leak

- When Monitored:
Engine speed is above 550 RPM and has been for more than one second and the total effective throttle area is above a certain threshold (mapped against engine speed).

- Set Condition:
The mass air flow value (g/s) of sensor 1 does correlate with the estimated mass air flow value for sensor 1 and the mass air flow value (g/s) of sensor 2 does correlate with the estimated mass air flow value of sensor 2 and the manifold pressure sensor value (kPa) is greater than and does not correlate with the estimated manifold pressure value. One Trip Fault. Three good trips to turn off the MIL.

Air Restriction

- When Monitored:
Engine speed is above 550 RPM and has been for more than one second and the total effective throttle area is above a certain threshold (mapped against engine speed).

- Set Condition:
The mass air flow value (g/s) of sensor 1 is lower than and does not correlate with the estimated mass air flow value for sensor 1 and the mass air flow value (g/s) of sensor 2 does correlate with the estimated mass air flow value of sensor 2 and the manifold pressure sensor value (kPa) does correlate with the estimated manifold pressure value. One Trip Fault. Three good trips to turn off the MIL.

OR

The mass air flow value (g/s) of sensor 1 does correlate with the estimated mass air flow value for sensor 1 and the mass air flow value (g/s) of sensor 2 is lower than and does not correlate with the estimated mass air flow value of sensor 2 and the manifold pressure sensor value (kPa) does correlate with the estimated manifold pressure value. One Trip Fault. Three good trips to turn off the MIL.

Undetermined Air Flow Rationality Fault

- When Monitored:
Engine speed is above 550 RPM for more than one second.

- Set Condition:
None of the above faults are active. The mass air flow value (g/s) of sensor 1 does not correlate with the estimated mass air flow value for sensor 1, or the mass air flow value (g/s) of sensor 2 does not correlate with the estimated mass air flow value of sensor 2, or the manifold pressure sensor value (kPa) does not correlate with the estimated manifold pressure value. One Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. DTC IS ACTIVE

NOTE: Diagnose and repair any Crank Sensor DTC, Cam Sensor DTC, reference voltage DTC, air intake system restriction or exhaust system restriction before continuing with this test.

1. Turn the ignition on.
2. With the scan tool, select View DTCs and review the DTC environmental information.

Is the good trip counter greater than 0?

Yes

- Perform the CHECKING FOR AN INTERMITTENT DTC diagnostic procedure. Checking for an Intermittent DTC.

No

- Go To 2

2. CHECKING THE MAP SENSOR OPERATION

NOTE: Diagnose and repair any MAP sensor, MAF sensor, IAT sensor, coolant sensor, baro sensor, or throttle position sensor circuit DTCs before continuing with this test.

Perform the diagnostic procedure for CHECKING THE MAP SENSOR OPERATION. Checking the MAP Sensor Operation.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 3

3. CHECKING THE THROTTLE POSITION SENSORSPerform the diagnostic procedure for CHECKING THE THROTTLE POSITION SENSORS. Checking the Throttle Position Sensor.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Perform the CHECKING FOR AN INTERMITTENT DTC diagnostic procedure. Checking for an Intermittent DTC.