what caused my eec to burn out a resistor (pic)

[turbo94gt]

hey guys just trying to figure out some horrible rough idle and running issues with my fox. did a load of troubleshooting but havent checked over entire harness for shorts. did some tests on pin 46 on eec then opened up eec to find this. you can see the one resistor in the middle is white and burnt up.

what could cause this?

thanks guys

 

[Bullitt347]

Sometimes stuff just wears out. Usually is associated with a bad ground or a short to power. The resistor was loaded beyond it's limit or after years of use, it reached the end of it's ability to do what it was designed to do.

 

[turbo94gt]

thanks for the reply can those bad grounds or short to power be anywhere on the harness?

 

[65ShelbyClone]

Resistors are one of the least likely discrete components to wear out, though. They usually fail from current overload. The solder in turbo94's ECU appears to have melted as a result.

Can you take a photo of the bottom of the pcb and indicate where the burned resistor's leads are? The idea is to follow the traces it connects to out to the harness plug, if applicable.

 

[turbo94gt]

can prolly get a pic for you tommorow as the ecu is at my friends house. but that is a great idea to follow the leads out to the ecu harness connector. i will try to follow

 

[jrichker]

What did the damage? Here's the likely answer...

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

Here's the fix for many of the damaged computers...

Remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the black/white wire and pin 46 on the computer wiring connector: it should be less than 1.5 ohms. More that 1.5 ohms is a wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1.5 ohms. More that that and the computer’s internal ground has failed, and the computer needs to be repaired or replaced.

See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix for the computer internal signal ground.