Electro-Hydraulic Power Steering (EHPS)

U1601-00-ECU APPLICATION SOFTWARE CODE 1 MISSING OR CORRUPTED

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation
The Electro-Hydraulic Power Steering (EHPS) Pump assembly contains a control module, brushless electric motor, and hydraulic pump integrated into a single unit. The EHPS Pump draws power from the 12-Volt electrical system and provides the necessary flow and pressure to the steering gear to provide normal power steering. The EHPS Pump requires communication over the CAN C bus to function properly. The output flow of the EHPS Pump is varied as a function of Steering Wheel Rate (received from SAS) and Vehicle Speed (received from ABS Module) in order to provide the optimum flow of power steering fluid to the steering gear under all operating conditions. The EHPS Pump will start to provide steering assist when the Vehicle speed message greater than 5 km/h (3 mph) is received on CAN C. If the Vehicle Speed message is missing at vehicle startup, the EHPS Pump will not operate. If the Vehicle Speed message is lost during operation the EHPS pump will use a default vehicle speed of 85 km/h (59 mph) to calculate desired flow and as a result, steering effort will no longer be speed sensitive. If the Steering Wheel Position message is lost the EHPS Pump will use a default steering wheel rate of 230°/sec to calculate desired flow and as a result, steering effort may be higher on evasive steering maneuvers. The EHPS pump will resume normal operation automatically once any missing message or out of range condition noted above is restored to normal.
- When Monitored:
Continuously, with the ignition on.

- Set Condition:
When the Electro-Hydraulic Power Steering (EHPS) Pump detects that its software has been corrupted or is missing.





CHECK FOR DTC U1601-ECU APPLICATION SOFTWARE CODE 1 MISSING OR CORRUPTED

NOTE: This DTC must be active for the results of this test to be valid. Check for a loose scan tool connection. Verify battery charger is installed and charge rate provides approximately 13.5 volts.

1. Ignition on, engine off.
2. With the scan tool, read the DTCs.
3. With the scan tool, follow the reprogramming procedure and reflash the Electro-Hydraulic Power Steering (EHPS) Pump while maintaining voltage as noted above.
4. With the scan tool, read the DTCs.

Does the scan tool display: U1601-00-ECU APPLICATION SOFTWARE CODE 1 MISSING OR CORRUPTED?

Yes

- Replace and program the Electro-Hydraulic Power Steering (EHPS) Pump. Power Steering Pump - Removal.
- Perform EHPS VERIFICATION TEST. EHPS Verification Test

No

- The conditions that caused this code to set are not present at this time. Using the wiring diagram/schematic as a guide, inspect the wiring harness and connectors.
- Perform the EHPS VERIFICATION TEST. EHPS Verification Test