MSefi.com read only forum (Jan.15,2018)

MSII Ver. 357. Using relay board and GM IAT sensor. Noticed my reading is always stuck at 70 deg. no matter what. Connected the stim and the readings vary with the pot adjustment so it is not the ECU. Disconnected the two wires from the sensor where they connect at the relay board and I get the steady 70 deg. I would guess that the problem is either in the relay board or the cable between the relay and the ECU? What I found a little strange is that with the stim connected, if you dial the pot to the highest setting, it gives the same result - constant 70. The temp will climb with the pot to what I suppose is the max. and then goes to 70 and stays there. Does this mean anything or is this normal and I just have a bad relay or cable?
Thanks,
Paul

On the stimulator with the pot at the higher settings you'll hit the "failsafe" This is the value MS recognizes as sensor/input failure and a value (mine is 180*F) is substituted to keep the engine running. If your CLT reading is ok you might try removing its connector and jumping it to the IAT sensor. If you get a reading close to your CLT reading (cold engine) than you'll know your IAT sensor is ok and you have a wiring problem.

Does this mean anything or is this normal and I just have a bad relay or cable?

The relay board just feeds the IAT wiring straight from the 20 pin terminal strip to the DB37, no relays involved.