ofelas

Hi,

Does this randomly. Grid heaters work as does the WIF sensor.

Overdrive off switch clicks & lights as usual, but no OD sometimes.

When this happens, the water in fuel & wait to start lamps light steadily & sometimes flash.

Its a 91.5 with no crank sensor or tach plug, and an ECM with an external regulator.

Truck doesn't have AC or cruise.

Thx!

j_martin

Check power and grounds to the PCM.

ofelas

Voltage on pin 55 and continuity on the ground pin ?

j_martin

There's at lease 2 B+ pins, and several grounds, power and signal. I don't have my SM with me right now.

ofelas

I have a 91 FSM, but I believe wiring changed a bit on the 91.5 intercooled trucks, will have to try and get more info...
By the way - there are 2 sensors vertically screwed into the intake manifold, one for Intake air temp & the second for the KSB signal I believe.
Where would the thermos witch that controls OD be at ? I hear it could be on 2 locations, screwed horizontally on the cylinder head/block junction near the fuel filter/lift pump, or in a tranny line...depending on 91 or 91.5 or 92...