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!

What is the code?

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.