I have a 1999 Olds Bravada that is blowing the ECM1 fuse in the under hood fuse panel. Anyone got some ideas on what can be causing this? Fuse is 15 amp rated.

 

The ECM1 fuse powers the ICM (ignition control module), PCM (powertrain control module), CKP (crankshaft position) sensor, CSFI (central sequential fuel injection) unit, and the ignition coil all through circuit .

A short to ground anywhere on this circuit could cause the fuse to blow as could any one of these components having an internal problem.

I would disconnect the coil first and then the ICM next and see if the fuse still blows.

 

We have already replaced the coil as I wasn't happy with the resistance between the secondary and primary coil windings. It ran great for a few days then started again. I haven't completely traced out all of the wiring yet but that is my next move. Hope it ins't the ECM but that is a thought to keep in mind. Thanks.

 

Welcome from a land far, far away!

 

This is an update to the 1999 Olds Bravada ECM fuse question. I am actually working on my mother-in-law's vehicle and have just found out that it is actually a 2000 model. Does anyone know where I cam find and accurate schematic that will show everything powered by this Fuse? The help will be appreciated.

 

A 2000 is the same as I have listed previously. From the sounds of it, you have a short in the harness.

 

Thanks swartlkk. I have already opened the harness most of the way and found nothing and read no shorts to ground on any of the wires incolved. The insulation on many of the wires in the harness were stuck together and I seperated them and the vehical now starts but the way it is failing would seem to indicate a component breaking down after a certain amount of time under load. I worked in electronics for over 30 years and saw this a lot. The problem is that it only seems to fail when it is running and disconnecting most of what is powered by this fuse will not permit the car to fire. I also traced one of the pink wires from this breaker to the gismo that is just behing the air filter in the intake, I am not sure what it is called. Ran the truck for almost an hour yesterday with no problems but I know it probably isn't fixed. Thanks for the info.

 

*Moving to 2nd Gen Tech* - I'm not sure how I missed this... I also updated the thread title.

Are you equiped to back probe the connections and measure voltage drop across the circuit? Your problem could be with a wire or two that have corrosion inside the wiring causing a resistance. The voltage drop would increase as the wiring heats up to a point where the fuse would pop. Just another method of diagnosis I have had to employ in the past.

It sounds like you are either describing the IAT (intake air temp) sensor or the MAF (mass air flow) sensor. The MAF sensor is the large device that connects inline between the engine and the filter box. The IAT sensor is a little sensor that hooks into the side of the intake duct between the MAF and the engine. My diagrams do not list either of these two sensors as being powered by the ECM1 fuse though. The MAF sensor is powered through the ENG 1 fuse while the IAT sensor is powered directly from the PCM.