ABS Problem ('92 Accord EX-4dr, 2.2L MT)
#1
ABS Problem ('92 Accord EX-4dr, 2.2L MT)
Symptom: ABS Warning Light Continuously ON.
Background Troubleshooting: All ABS Fuses OK. Mitsuba (ABS) Motor Relay (12V NO, #218) seems to operate at ~12VDC. ABS Pump Motor runs if I jump the relay output leads. However, only ~ 5VDC shows at the coil-side of the Relay - from my troubleshooting, 5VDC is NOT enough to actuate the Relay.
Question(s):
1) A)Should there be ~12VDC at the coil-side of the Relay when the ignition key is in the ON position? B) And/or should there be ~12VDC at the coil-side of the Relay when the car is started? C) And/or should there be ~12VDC at the coil-side of the Relay only when the brakes are actuated?
2) If there IS supposed to be ~12VDC at the coil-side of the Relay during one of the above times (1 A, B or C), does that imply that the ECU is limiting the Relay's coil-side voltage to (perhaps) protect the ABS Pump Motor? And, if so, what would cause the ECU to limit the voltage - One or more "bad" axle pickup sensors?
3) I looked for the ECU, per some threads' description of location, but am unable to find it; thus, I cannot determine the Error Code(s).
Thanks!
Background Troubleshooting: All ABS Fuses OK. Mitsuba (ABS) Motor Relay (12V NO, #218) seems to operate at ~12VDC. ABS Pump Motor runs if I jump the relay output leads. However, only ~ 5VDC shows at the coil-side of the Relay - from my troubleshooting, 5VDC is NOT enough to actuate the Relay.
Question(s):
1) A)Should there be ~12VDC at the coil-side of the Relay when the ignition key is in the ON position? B) And/or should there be ~12VDC at the coil-side of the Relay when the car is started? C) And/or should there be ~12VDC at the coil-side of the Relay only when the brakes are actuated?
2) If there IS supposed to be ~12VDC at the coil-side of the Relay during one of the above times (1 A, B or C), does that imply that the ECU is limiting the Relay's coil-side voltage to (perhaps) protect the ABS Pump Motor? And, if so, what would cause the ECU to limit the voltage - One or more "bad" axle pickup sensors?
3) I looked for the ECU, per some threads' description of location, but am unable to find it; thus, I cannot determine the Error Code(s).
Thanks!
#3
Found the Service Check Connector, behind glove box. Followed Manual's instructions to the letter (ignition OFF; short connector; ignition ON), but ABS Indicator Light refuses to cooperate - no blink(s); solid yellow. Suspect ABS control unit is culprit, or Service Connector has an open between either/both the ECU and ACU.
In any event, measured Resistance values for all axle sensors from pulled 18Pin ACU connector. Front right and left were both good at ~ 900 Ohms/infinite to chassis. But 500K-Ohms to chassis ground found at both rear axle sensors (resistance measured between +/- was good at ~1300 Ohms for both left and right rear, but resistance to chassis was not infinite at either) - infinite resistance would be better. Note that once I disconnected the actual right axle sensor from the circuit, the left rear sensor did go to infinite-to-chassis. Suspected wiring harness, but then remembered rear sensors may be tied internally to each other at ACU.
Will determine if Service Check Connector has a wiring problem, and advise Code(s). Any thoughts in the meantime would be appreciated.
Thanks.
In any event, measured Resistance values for all axle sensors from pulled 18Pin ACU connector. Front right and left were both good at ~ 900 Ohms/infinite to chassis. But 500K-Ohms to chassis ground found at both rear axle sensors (resistance measured between +/- was good at ~1300 Ohms for both left and right rear, but resistance to chassis was not infinite at either) - infinite resistance would be better. Note that once I disconnected the actual right axle sensor from the circuit, the left rear sensor did go to infinite-to-chassis. Suspected wiring harness, but then remembered rear sensors may be tied internally to each other at ACU.
Will determine if Service Check Connector has a wiring problem, and advise Code(s). Any thoughts in the meantime would be appreciated.
Thanks.
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11-07-2013 07:10 AM