Going Crazy... ECM 1 fuse Blows! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cwgrl · 07-17-2013, 10:12 AM

Hi all,

I can't find my problem, and I'm going crazy. 1990 V2500, normally run perfect. :-)

On the road last week, and it died. get it home, check fuses... ECM 1 blown. replace..turn key to On position... blows again.

Before the blow, I can hear fuel pump relay click but no fuel pump prime. I changed the relay anyway.

I have traced wiring, everything seems OK. Did the process of elimination with sensors, unplug/plug in... still blows.

What am I missing?

HELP! :-) please Thank you!

Cape Codder · 07-17-2013, 12:51 PM

Does the fuse blow with the fuel pump relay out? If not the next step would be to put the relay back in and unplug the fuel pump and see if the fuse blows. Good luck

Bob

cwgrl · 08-08-2013, 01:12 PM

I have traced every pink/blk wire I can find and as of this moment here is what is unplugged.

Injectors, Map, IAC, EGR solenoid, ESC, ECM, O2, Tranny, Fuel pump, relays, oil pressure sending unit, TPS, Coolant temp gauge, no radio, no dome lights, dash gauges completely unplugged, alternator, kickdown switch, and any pink/blk plug under dash.

I also removed distributor, and coil. check harness against firewall, all looks good.

Still blows fuse! Maybe, fuse panel?

CrazyDave · 08-08-2013, 01:29 PM

My 91 K2500 did that couple years back and I had to replace the ECM

speedygonzales · 08-08-2013, 01:31 PM

Use your VOM to find it. First set it to voltage and measure both contacts for the fues in question. The fuse must be out. One side has 12 volts the other side has nothing. Now set your VOM to ohms low setting if you can choose it. Like 200 ohms. Put one lead in the contact that had no voltage and the other lead to ground. There should be an infinite reading (digital VOMs use OL).

If yours is a short to ground, it will read low ohms like below 1 ohm. Leave the meter the way it set up and begin to wiggle every wire you find from the fuse holder to the other end of the wiring in question. If you find the spot causing the problem, the meter will change to a much higher reading.

Start by looking at locations where the wiring either passes through a hole in a panel or bends around a corner.

07-17-2013, 10:12 AM	#1
cwgrl Registered User Join Date: Jun 2005 Location: SoCal Posts: 3	Going Crazy... ECM 1 fuse Blows! Hi all, I can't find my problem, and I'm going crazy. 1990 V2500, normally run perfect. :-) On the road last week, and it died. get it home, check fuses... ECM 1 blown. replace..turn key to On position... blows again. Before the blow, I can hear fuel pump relay click but no fuel pump prime. I changed the relay anyway. I have traced wiring, everything seems OK. Did the process of elimination with sensors, unplug/plug in... still blows. What am I missing? HELP! :-) please Thank you!

07-17-2013, 12:51 PM	#2
Cape Codder Registered User Join Date: May 2013 Location: Centerville,Ma. Posts: 1,224	Re: Going Crazy... ECM 1 fuse Blows! Does the fuse blow with the fuel pump relay out? If not the next step would be to put the relay back in and unplug the fuel pump and see if the fuse blows. Good luck Bob

08-08-2013, 01:12 PM	#3
cwgrl Registered User Join Date: Jun 2005 Location: SoCal Posts: 3	Re: Going Crazy... ECM 1 fuse Blows! I have traced every pink/blk wire I can find and as of this moment here is what is unplugged. Injectors, Map, IAC, EGR solenoid, ESC, ECM, O2, Tranny, Fuel pump, relays, oil pressure sending unit, TPS, Coolant temp gauge, no radio, no dome lights, dash gauges completely unplugged, alternator, kickdown switch, and any pink/blk plug under dash. I also removed distributor, and coil. check harness against firewall, all looks good. Still blows fuse! Maybe, fuse panel?

08-08-2013, 01:29 PM	#4
CrazyDave Registered User Join Date: Nov 2011 Location: Berlin, Kentucky Posts: 72	Re: Going Crazy... ECM 1 fuse Blows! My 91 K2500 did that couple years back and I had to replace the ECM __________________ David Fultz - Berlin Ky 79 K5 2wd - Project 86 GMC 1500 LWB- Shop Truck 84 Chevy K-20 Hugger Orange and Silver- Wifes Truck 2018 Ram 2500 - Tow Rig 79 Chevy C-30 SRW- Bought new by Uncle

08-08-2013, 01:31 PM	#5
speedygonzales Registered User Join Date: Jan 2006 Location: Smithfield, VA Posts: 1,501	Re: Going Crazy... ECM 1 fuse Blows! Use your VOM to find it. First set it to voltage and measure both contacts for the fues in question. The fuse must be out. One side has 12 volts the other side has nothing. Now set your VOM to ohms low setting if you can choose it. Like 200 ohms. Put one lead in the contact that had no voltage and the other lead to ground. There should be an infinite reading (digital VOMs use OL). If yours is a short to ground, it will read low ohms like below 1 ohm. Leave the meter the way it set up and begin to wiggle every wire you find from the fuse holder to the other end of the wiring in question. If you find the spot causing the problem, the meter will change to a much higher reading. Start by looking at locations where the wiring either passes through a hole in a panel or bends around a corner. __________________ 99 Z71 (98 body style) Pride and joy



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