P1550

Stepper Motor Cruise Control Diagnostic Chart:

Stepper Motor Cruise Control Wiring Schematic:

CIRCUIT DESCRIPTION
The stepper motor cruise (SMCC) system differs from the up integrated (Powertrain Control Module (PCM) - controlled) cruise system previously used in that it is a stand-alone system. The PCM still retains the ability to disable cruise if conditions are detected which would make cruise control operation undesirable. The following conditions may cause cruise control to be inhibited by the PCM: Engine not running long enough for cruise operation; Diagnostic Trouble Codes P0705 OR P1630 set: Engine speed too high or too low: Vehicle speed too high or too low: trans range input indicates park, neutral, low, or reverse gear selected. If the PCM detects any of these conditions, it will interrupt the ground at the cruise status signal (CKT 85) to request that cruise control be disengaged.

DIAGNOSTIC TROUBLE CODE (DTC) P1550 WILL SET WHEN
The cruise status signal (CKT 85) indicates an open or a short to voltage while cruise is engaged and vehicle speed below 7 mph.

ACTION TAKEN (PCM WILL DEFAULT TO)
DTC P1550 does not illuminate the Malfunction Indicator Lamp (MIL) (Service Engine Soon).

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

1. Ensures that the PCM is detecting a current fault.
2. Ensures that CKT 85 is not open or grounded, or shorted to voltage, and CKT 85 is being switched "ON" and "OFF" by the SMCC (I) module.

DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Check For:

Poor Connection or Damaged Harness
Inspect PCM harness for open or short to voltage in CKT 85, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

Intermittent Test
Observe SMCC (I) status on Tech 1 while moving related connectors and wiring harness with engine running. If the failure is induced, the SMCC (I) status display will change to engaged. This may help to isolate the location of the malfunction.

SMCC (I) is a stand alone system, once the software has seen a valid cruise engagement, it has learned cruise is on the vehicle.