Circuit Description
The PCM will not allow cruise control operation under certain conditions, for example, vehicle speed is too low. This is done by the PCM grounding the 12 volt cruise inhibit signal (CKT 83) sent by the cruise control module. If the PCM is allowing cruise operation and the customer requests cruise, the cruise control module will ground the cruise engaged signal (CKT 396) to the PCM. This diagnostic is used to compare the cruise inhibit output versus the cruise engaged input. If the PCM detects that the cruise control module is signaling that it is engaged by grounding CKT 396 while the PCM is inhibiting cruise operation on CKT 83, DTC P1554 will set.
Conditions for Running the DTC
The PCM is sending out a cruise inhibit signal.
Conditions for Setting the DTC
The PCM monitors a signal that cruise is engaged.
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will not illuminate. |
| • | No message will be displayed. |
Conditions for Clearing the DTC
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test. |
| • | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. |
| • | Use a scan tool to clear DTCs. |
| • | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Powertrain Control Module Description . |
Diagnostic Aids
Both the Cruise Engaged and the Cruise displays can be monitored at the same time to aid in diagnosing an intermittent fault.
Clear the DTC and operate the vehicle under the conditions in which the DTC set if a fault condition is suspected.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
2 | Is DTC P0503 also set? | -- | Go to Automatic Transmission for diagnosis | Go to Step 3 |
3 | Since most occurrences of DTC P1564 are caused by wheelspin due to icy, wet or slippery conditions, check with the customer to verify the conditions under which the DTC set. Did the road conditions cause this DTC to set? | -- | Go to Step 4 | Fault not present. Refer to Diagnostic Aids |
4 | Explain system operation to the customer and clear this DTC. Is the repair complete? | -- | System OK | -- |
