Circuit Description
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The electro-hydraulic power steering (EHPS) module communicates with the vehicle by means of the controller area network (CAN) database. The connector has 2 pins for CAN-high and two pins for CAN-low communications. No class 2 messages are received or sent on the vehicle database. The EHPS will read CAN messages from the powertrain control module (PCM), hybrid control module (HCM) and energy storage control module (ESCM). The PCM will act as the gateway to translate CAN messages into class 2 messages when required for diagnostic purposes.
The EHPS module receives the following messages from the CAN bus:
- Vehicle speed (direct signal in km/h)
- Service disconnect status
- PRNDL (shift lever) position
- TCC/Cruise Dump signal (gives zero-adjust brake switch position)
The EHPS module sends the following message to the CAN bus:
- Brake pedal rate, position, in-range rationality and out-of-range diagnosis
- EHPS module status
- Diagnostic messages to DIC via PCM (EHPS module state: OK, Service Brake, Service Steer, fault)
- Diagnostic information requested by service technicians via Tech 2 link (class 2 via PCM)
- Steering wheel sensor diagnostic message (in-range, out-of-range failure)