JA,
ABS Module is same OVP power feed as MAS/ECU ...so , a quick test is to look for ABS lamp default, indicating OVP feed problem. Knowing this is the same feed, the Tech is simply using the ABS lamp default as a power glitch/interruption detector tool. So, if one sees a post responce asking "ABS lamp ON ? " , OVP diagnosis is where we are heading.......
The orig OVP was a Siemens and they were a problem , so the replacement was a redesign.
Very Common on models thru 95 w/IL-6.
The chassis you are working on will still run manual/less electric controls /closed-loop w/bad OVP , but if you get any later HFM /SFI -full electronic ones ,[ 93-95] they will not b/c they are fully computized engine management dependent.

So, an ABS lamp coupled with a start/run complaint on either system [ 103/104] is a quick tip-off that first suspect is a faulty OVP relay.....so common a fail rate that we keep a " TEST OVP " in the tool box for a time saving swap test instead of DMM tracing.
If you have no test relay available, sometimes a few relay taps will indicate the relay also...but not always.

PS ..I see the TTS problem was resolved @113. He left a nicely written responce........

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A Dalton