P071

Circuit Description

This diagnostic test monitors Throttle Position (TP) sensor, Engine Speed, Manifold Absolute Pressure (MAP), EGR Flow, and Air Conditioning (A/C) Clutch status. Engine operation requires that a large change in manifold pressure must be preceded by a change in engine load due to changes in throttle angle, engine RPM, EGR flow or A/C clutch status. If TP sensor, engine rpm, EGR Flow, and A/C Clutch remain constant, and there is a rapid change in MAP, PCM Code P071 will set.

Test Condition(s)

1. Code P021 and P022 not set.
2. Throttle Position (TP) sensor does NOT change more than 1 degree for 1.01 seconds.
3. Engine Speed is greater than 500 RPM and does not change more than 100 RPM for 1.01 seconds.
4. EGR does NOT change more than 4% for 1.01 seconds.
5. Air conditioning clutch must stay 'ON' or 'OFF' during test (cannot cycle).
6. Low coolant level and engine overheat not present.
7. Traction control not active.
8. PCM receiving reference pulses from ICM at least every 0.3 second.

Failure Condition(s)

MAP Sensor reading changes more than 6.3 kPa in 12.5 milliseconds.

Action Taken

PCM uses a substitute MAP value based on engine RPM and throttle position switch status.

NOTES ON INTERMITTENTS:

1. Checking if the MAP sensor can read barometric pressure correctly (85 to 105 kPa).
2. Checking the MAP sensor ability to react to a known vacuum (26 to 34 kPa).
3. Checking the MAP sensor's ability to react to a sudden change in vacuum.