'94 E320 Cab. intermittent ASR/ABS lights on. First, Both come on. After that, only ASR light. Takes about 5 or so minutes to light up.

Impulse code 2..L/F speed sensor. Pulled first time & cleaned. reset lights & was O.K. for a few days. Then, Same thing. Replaced OVP relay, reset everything & O.K. for a few days again.

Occasionaly, while testing with engine running and waiting for lights to indicate fault, will hear ABS pump run for about 90 seconds.

put Voltmeter to battery with engine running and get a variety of readings from 13.64 - 13.21 volts. The longer engine runs, the progressively lower the volts reading.

could this be as simple as Alt. going bad?