P1789
Symptom: Drop in engine idling speed when the selector lever is moved from P or N.
Selector lever position signal (R; D; 3, 2, 1), DRIVE signal, open circuit or shorted to ground.
Fault symptom
Drop in engine idling speed when the selector lever is moved from P or N.
Condition
Shorting to ground or open circuit.
Check the wiring
Intermittent faults may occur as a result of temporary short circuits and breaks in the wiring. Jiggle the leads at several places and in different directions to reveal any faults in the wiring harness, including connectors. Observe the multimeter, test lamp or ISAT scan tool while carrying out this check.
Diagnostic procedure
1 Check the transmission control module's output signal
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Connect the Scan tool diagnostics instrument.
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Turn the ignition switch to the ON position.
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Select "DRIVE". The diagnostics instrument should show OFF when the selector lever is in position P or N and ON when it is in position R, D, 3, 2 or 1.
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Is the reading correct?
Continue with point 4.
Continue with point 2.
2 Check the engine management system's input signal
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Unplug the connector from the engine management system's control module.
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Turn the ignition switch to the ON position.
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Connect a test lamp to the connector as follows:
M4.1:
to pins 86 and 58
M5.2:
to pins 69 and 54
Saab Trionic:
to pins 14 and 60. The test lamp should light up when the selector lever is in the P and N positions and remain off in the other positions.
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Is the signal OK?
Continue fault diagnosis as described in Service Manual 2:7 "Engine management system" and then continue with point 4.
Continue with point 3.
3 Check the wiring
Check the wiring for continuity between the transmission control module and the engine management system.
Is the wiring OK?
Continue with point 4.
Rectify the fault and continue with point 4.
4 Final check
Drive the car on test and check whether the fault symptom persists.
Does the fault symptom persist?
Continue with
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The remedial action taken was correct.
