93 Cutlass 3.4 DOHC .... ECM 10A fuse blows

[chriswhewell]

As the title suggests...... I've replaced the 10A fuse for the ECM for the third time in the past year. Each time, I put in a new fuse and it runs just fine.

This last fuseblow occurred at the instant I very quickly punched the accelerator.

So, all I can think of, is maybe a fuel injector that has a too-low resistance and its drawing too much current ?

[pocket-rocket]

I would almost think that if that were the case the ECM itself could be damaged, but it is a possibility.

Have you ohmed out the injectors? The front 3 are accessible without pulling the intake. You could also unplug the injector harness from the engine bay harness and ohm the 2 banks that lead to it to see how much they vary since they are wired with 3 injectors on one "channel". Both are wired into one driver in the ECM internally, but outside of the ECM it's two. Measuring the difference between the two could help to find out if one is shorted since there would be a decent difference in resistance between the two sets.

[chriswhewell]

I would almost think that if that were the case the ECM itself could be damaged, but it is a possibility.

Have you ohmed out the injectors? The front 3 are accessible without pulling the intake. You could also unplug the injector harness from the engine bay harness and ohm the 2 banks that lead to it to see how much they vary since they are wired with 3 injectors on one "channel". Both are wired into one driver in the ECM internally, but outside of the ECM it's two. Measuring the difference between the two could help to find out if one is shorted since there would be a decent difference in resistance between the two sets.

Yes, but I only checked the front three injectors, they were all within normal resistance values. I noticed that someone at some point did however replace one of the three i'd examined. Car only as 70k on it but age can take its toll and the injectors need swappin anyhow. I'll probably go with John at fuel injector connection .com I think a set was only like $170 or so and the technology has come a long way since '93. I just need to budget a couple hours to do the job, but was also looking for any other thoughts on why that 10amper might blow....injector is all I can figure at this point.

[pocket-rocket]

Hopefully robertisaar will chime in on this. He can get you a wiring diagram so you know what else that fuse powers.

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[chriswhewell]

Hopefully robertisaar will chime in on this. He can get you a wiring diagram so you know what else that fuse powers.

Sent from my HTC One X using Tapatalk 2

Thanks aolt. I love that motor, just need to find a trans that can handle it once I put the valve timing and fueling back to optimal.

[robertisaar]

there are a couple labeled as "ECM":



underhood on the driver's side near the strut tower, labeled as "FUEL/ECM", 20 amps, used for ECM(pin D17), fuel pump relay(load portion) and oil pressure switch/sensor.

instrument panel fuse block, "ECM", rated at 15 amp, only used for the ECM, pin B10.



sounds like you have the wrong sized fuse stuck in at least one of them for some reason.

[chriswhewell]

there are a couple labeled as "ECM":



underhood on the driver's side near the strut tower, labeled as "FUEL/ECM", 20 amps, used for ECM(pin D17), fuel pump relay(load portion) and oil pressure switch/sensor.

instrument panel fuse block, "ECM", rated at 15 amp, only used for the ECM, pin B10.



sounds like you have the wrong sized fuse stuck in at least one of them for some reason.

Dang it, I'm so sorry. Its the "DIS" fuse, 10A. I searched both volumes of the repair manuals, and the internet, for just what the H the DIS fuse is. Sounds like distributor or maybe electronic spark but couldn't find it in any of the circuit diagrams or the description. It blew out right when I made a near-instantaneous torque request.

[pocket-rocket]

DIS stands for Distributorless Ignition System. It uses 3 coil packs to fire 3 pairs of cylinders. I'm not certain if that's on its own circuit by itself or if it's a shared fuse. It could be your ignition module is going bad, or possibly a chafed wire (not plug wire, but engine harness) grounding out when the engine rocks from the power, a bad coil pack. Can you take the ignition module out and have it tested? It lives behind the coil packs and almost any parts store chain can test it.

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[robertisaar]

at least that's easier to diagnose. and is 10 amps too.

DIS fuse only powers the ICM and it's attached items(namely, the coil packs).

i'd say either your ICM or a coil pack is doing it. maybe more than one coil pack. the wiring could also be suspect as Jon mentioned.

[chriswhewell]

at least that's easier to diagnose. and is 10 amps too.

DIS fuse only powers the ICM and it's attached items(namely, the coil packs).

i'd say either your ICM or a coil pack is doing it. maybe more than one coil pack. the wiring could also be suspect as Jon mentioned.

I bought the car about 2 months back and it wasn't running at the time. Traced the trouble to a bad module, and put a new one in it and ir fired right up. During the course of the fun, I re-located the coil pack and module to the front passenger corner of the veh where the alarm horn previously was. The stock mounting location is subjected to unnecessary heat, and now when I need to inspect the system its a snap. I guess I'll pull the coils and check their resistance, but they tested fine a month ago. Plus the previous owner had reported blowing that fuse also. I've driven it half an hour with a 15 amp fuse in place of the 10, then once I made it home I put a 10 back in. Maybe I'll just replace all three coils.

[pocket-rocket]

Yeah, ever since I've had mine I've never liked where they were put from the factory. Stupidest place ever...

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