Testing Notes
PINPOINT TEST QCODES: C1194, C1198, C1200, C1210, C1212, C1214, C1216, C1242, C1244, C1246, C1248, C1250, C1252, C1254, C1256
Normal Operation
The ECU conducts a valve function test every time the vehicle is keyed on and the wheels exceed 4 MPH for the first time. If valve function is verified, the ABS system is enabled. During normal driving, the power relay is pulled in every time the brake is applied enabling the valves to function if required. A passive check is conducted by the ECU to check for open valve solenoids at this time.
Fault Description
Open ISO valve, and shorted ISO valve, are generated by the microprocessor's detection of an internal low feedback voltage when the FL ISO valve is supposed to be off or detection of an internal high feedback voltage when the FL ISO valve is supposed to be on. Both codes can be generated by the ECU during the 4 MPH valve check or during ABS activation. Once a valve fault is detected, the yellow ABS lamp is turned on and the system is disabled for the remainder of the ignition cycle. Upon the next ignition cycle, if the fault is not present, the system will function. However, the fault code is retained for 50 ignition cycles.
Possible Contributing Components/Vehicle Wiring Concerns
- Open/shorted valve solenoid
- Shorted/open EHCU valve driver
- Defective valve feedback circuit within EHCU