Circuit Description
The stepper motor cruise module communicates with the powertrain control module (PCM) over three circuits (cruise engaged, cruise disabled, and vehicle speed sensor (VSS) output). The cruise enable status tells the PCM if the cruise control system is enabled. The VSS output is the speed signal from the vehicle speed sensor through the PCM and used by the cruise control module. The cruise disable line allows the PCM to disable cruise under the various conditions described below:
| • | DTCs P0122, P0123, P0200, P0335, P0502, P0562, P0563 not set. |
| • | Engine is not running. |
| • | Transmission is in park, neutral or reverse (auto trans.). |
| • | Transmission is out of gear (manual trans.). |
| • | Safety fuel cut-OFF is active. |
| If the PCM detects any one of the above conditions, it will interrupt the ground at the cruise disable input circuit and disable the cruise control. |
Diagnostic Aids
| • | This table will not diagnose any cruise control system circuits other than those connected to the PCM. For diagnosis of the remaining circuits, refer to Wiring Repairs in Wiring Systems. |
| • | An Intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside the insulation. |
| • | The cruise control system may disable if actual speed is less than 24 km/h (15 mph) than commanded vehicle speed, i.e. towing a trailer, or climbing a steep grade. |
| • | Minimum vehicle speed for setting the cruise control system is 40 km/h (25 mph). |
Test Description
The numbers below refer to the step numbers on the diagnostic table:
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The cruise speed set has to be above the minimum speed 40 km/h (25 mph) required for cruise operation. Drive vehicle in an area where enough room is allowed for cruising.
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If the vehicle was in the enabling criteria for cruise operation, the PCM should have read stepper cruise Engaged even if cruise was not requested. The cruise engaged circuit provides a ground to the cruise control module. This step tests for an open or shorted cruise engage circuit.
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At this point, the PCM is allowing cruise operation and the cruise module is telling the PCM that the cruise is engaged. If the vehicle will not maintain the set speed, then the malfunction is in the cruise control module, or is a throttle linkage problem.
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The replacement PCM must be programmed and the Crankshaft Position System Variation Learn procedure must be preformed.
Step | Action | Values | Yes | No | ||||||
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||
2 | Are any DTCs set? | -- | ||||||||
Does the cruise control operate normally? | 40 Km/h (25 MPH) | |||||||||
With the scan tool, observe the cruise (engage/disengaged) parameter. Does the cruise parameter display engaged? | -- | |||||||||
5 | With the scan tool, observe the cruise (engage/disengaged) parameter while performing the following:
Does the cruise (engage/disengaged) parameter display a change with each action? | -- | ||||||||
Does the DMM display a voltage near the specified value? | B+ | |||||||||
7 |
Did you find and correct the condition? | -- | ||||||||
8 |
Did you find and correct the condition? | -- | Go to Symptoms in Cruise Control | |||||||
9 |
Did you find and correct the condition? | -- | ||||||||
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Important:: The replacement PCM must be programmed.
Did you complete the replacement? | -- | -- | ||||||||
11 | Operate the vehicle within the conditions under which the original symptom was observed. Does the system now operate properly? | -- | System OK |
