Powertrain Controls - ECM/PCM

DTC 71 Chart:

*** Test Chart Revised per TSB # 41-65-37 ***

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 will set DTC 71.

DTC 71 WILL SET WHEN
- MAP sensor reading changes more than 7.4 kPa in 12.5 milliseconds.
- DTC21,22andii9notset.
- Throttle angle does not change more than 1 degree for 1.01 seconds.
- Engine speed does not change more than 100 RPM for 1.01 seconds.
- EGR does not change more than 4% for 1.01 seconds.
- A/C clutch must stay "ON" or "OFF" during test (cannot cycle).
- Low coolant level and engine overheat not present.
- Traction control not active.
- PCM receiving reference pulses from IC module at least every 0.3 second.

ACTION TAKEN (PCM WILL DEFAULT TO)
- DTC 71 does not illuminate the Malfunction Indicator Lamp (MIL) (Service Engine Soon).
- PCM uses a substitute MAP value based on engine RPM and throttle position switch status.

DTC 71 WILL CLEAR WHEN
The fault no longer exists.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This check uses PCM "Snapshot" data to determine if MAP was out-of-range at the time of the fault. PCM Snapshot Data