Cruise Control Diagnosis. Cadillac Concours 1997

For 1990-2009 cars

This powertrain has a stepper motor cruise control (SMCC) system which closely approximates a stand alone system, except that the SMCC relies on the PCM to indicate that cruise control is allowed and then signals the PCM when engaged. This is accomplished by using a two wire link between the PCM and SMCC. These are called the Cruise Inhibit and the Cruise Engaged circuits. If the PCM will allow operation, refer to the Cruise Operation table, it signals the SMCC on the Cruise Inhibit circuit to allow cruise. Once cruise is engaged by the driver, the SMCC will continuously signal to the PCM that cruise is engaged using the Cruise Engaged circuit.

Refer to Cruise Control System Check in Cruise Control for information regarding the cruise system not related to PCM interaction.

#### Cruise Operation

Cruise Inhibit Conditions | Possible Stored PCM DTC(s) | Scan Tool Cruise Status | Action Taken by the PCM
--- | --- | --- | ---
Vehicle speed below 20 MPH | Normal disable condition | Disabled | Disabled until speed increases
Vehicle speed above approx. 110 MPH | Normal disable condition | Disabled | Disabled until speed decreases
Engine not running continously for 15 seconds | Normal disable condition | Disabled | Disabled until engine running long enough
Fault detected in either cruise circuit | P1554 or P1654 | Disabled | Disabled while DTC set
Engine Metal Overtemperature active | P1258 | Disabled | Disabled while DTC set
Vehicle Speed Sensor faults | P0502 or P0503 | Disabled | Cruise disabled for entire ignition cycle
Ignition voltage not within normal range | P0560 or P0563 | Disabled | Disabled while DTC set
Transmission not in Drive, Third or Second gear | P1520 or P1560 | Disabled | Disabled while DTC set
TCC, Stoplamp or Extended Travel Brake switch applied or fault | P0719, P0724, P1574 or P1575 (also possible EBTCM DTCs) | Disabled | Disabled while applied or DTC set
Undesirable Cruise condition present | P1564 or P1566 | Disabled | Disabled while DTC set
Traction Control active | P1570 | Disabled | Disabled while traction is active and/or DTC is set
If cruise is inoperative and no DTCs are set, drive the vehicle above the minimum allowed speed and check for the Cruise status to change to Enabled. If status does not change check the above inputs to the PCM that may be inhibiting cruise operation.