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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3359
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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I have a 1999 Qatar 4964 ex with a Detroit I have a computer

Customer Question

Hi I have a 1999 Qatar 4964 ex with a Detroit I have a computer problem .it started with a speed signal problem I think. We changed from a auto shift to an 18 DPS and installed a new vas and had to splice a piece of 2 strand wire to reach new trans.we had it reprogrammed and speedo worked well for weeks. The speedo acted up and I checked new wires and splices they looked ok but may have been to close to trans for heat so I replaced them being carefull to have good connections . The speedo worked agian then failed then worked and with no wire changes. Then one day later all engine life's came on and instant shut down.then no engine lites except the park indicator lite would come on with key and crank no start. I got a wire diagram and checked the 5 pin power supply to battery and it had 12.5 on two and good grounds as well. I checked the two inline fuses from power supply on fire wall as well as grounds there. One fuse was blown I replaced it and all systems were normal agian . It ran for a few hours and 30 mile into trip I got brief engine lites and fast shutdown. I checked the fuses agian and they were ok. I checked ing power to Ecm on 30 pin connector at pin 2-b which book shows to ing switch had 12.5 bat voltage. Last checked bat power and grounds at 5 pin connector of ecm and same 12.5 and .001-.003 grounds. When ing is turned on nothing but p and low air lite (when air went low). Crank no start. I have looked at all harnesses and connectors and all clean no suspects. I don't think speedo had any bearing to this as ecm would work with or without of corse but timing I'd suspect. I believe I have a bad ecm nothing happens when key on except once in 10 times a ck engine flickers once. The ecm is from 2003 so it was replaced once. I bought it fro original owners in 07 and have only put 100k or so on it. It has apx 850000 total miles. Have you seen anything like this and is there any other tests I can do? I have new ecm with same program coming over nite but I have a super load multi axle on and have to roll before permits expire and have police and escorts waiting etc etc. so any help would be welcome. I can give you a com ck if u have blanks or card number if not. Thanks Gregg XXXXXXXXX
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 1 year ago.

My name is ***** ***** I will assist you.

You are pretty much aong the right path. If you have good battery voltage going in and good grounds, then show a good ignition voltage going in with no check engine light at key on or just a flicker, the ECM has something wrong with it.

When you turn the key on, you should always get a check engine light to come one to indicate the ECM is on and a engine light to indicate that the engine isn't running. Once started, it goes right out. You stated that you have good power to the pins, but no light. That tells me ther ECM isn't working properly and needs to be checked, or in a tight situation as you are in, replaced so you can get going down the road and then do something with the old/current ECM later.

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Expert:  Jeremy replied 1 year ago.

Almost seems like what you are describing that either the EEPROM is bad or the injector drivers went out which will burn up the whole board. Are you getting any flash codes at all when the ECM is powering up properly?

Customer: replied 1 year ago.
I have already pulled old computer but wanted to be sure not to have to check any other wires. On back of computer 5 pin connector with two power and three grounds and 30 pin b3 for ing power which pin is start position for computer and should I check it? If speed sensor fails it won't take out a computer even if it shorts to ground.?? The speedo was working well when computer quit on last time. But no lites with key on just small flicker now and then and yellow lite only. Is 5 pin just 2 power and 3 ground. And should I verify start power to ecm. This truck had an auto shift so start wire was run to start solenoid on firewall instead of through auto shift computer but solenoid should give same power to ecm??? Thanks
Expert:  Jeremy replied 1 year ago.

Youre power and grounds should be the same whether the auto shift is there or not.

If the speed sensor fails, not it will not harm the ECM. Even if it shorts to power or shorts to ground the ECM will not be affected. What burns up ECMs is main power issues and shorts on the injectors and main harness.

When you turn the key on and all you get is a small flicker, then the yellow engine light, I would suggest putting a computer on it and testing the ECM to see what it shows on the voltage inputs/outputs and that the readings are normal. There could be a harness issue causing shorts on the main power connector causing the ECMs to burn out.