88 subaru gl with ecm issues

[derekdee]

Hey everyone. I got an 88 subaru gl that straight died on me one day. Not slowly, just wouldn't start. I had it towed to a friend's shop, where he determined it was the ecm that was malfunctioning. Had a dealership warrant his claim for an additional 100 bucks, apparently the coolant was reading 40 degrees from a cold start and it wasn't holding an idle, tough to start... They also mentioned I was missing the wiring from the ecm to the O2 sensor. Therefore, I replaced the ecm twice now, the first one was blown, the second has at least allowed me to idle and start the car alittle easier. I'm assuming that its having troubles starting and riding rough, jerky, throughout the gears, due to the lack in feedback from the sensor. Went out and bought a bosch oem replacement, yet after installing the sensor, noticed that the wiring had been replaced with some ghetto lead wire. My question, how do I rewire the ecm wire leading to the sensor which consists of a white wire and another wire encasing that with black casing on it, seeing the sensor wire only has one wire encased in the wire casing. My other question is why my driver side headlight went dime, the dash lights went out and the tail lights are dimmed too??? I checked all the fuses, they looked good, including the inline under the hood. I can replace those just for piece of mind, but would love to be riding legal seeing I got pulled over last night for the tails. Thanks.

[subynut]

First I would have the alternator checked. Make sure it's putting out the proper voltage. If the regulator in the alternator went bad and spiked, that could one reason why the first ECU fried.

As far as the O2 sensor goes, sounds like the o2 sensor was replaced with a BOSCH universal instead of the BOSCH OEM replacement. The wiring from the ECU to the connector under the hood is a shielded cable. The center wire (white) is the signal and the outer (black) is shielding that is only connected at the ECU end (prevents ground loops and reduces noise). The BOSCH o2 sensors may not have a shielded cable going to the sensor itself, which is ok since it is a short length of wiring. All you need to connect it up is the signal wire from the O2 sensor and connect it to the center wire (white) on the harness. Do not use the outer wiring.

 

Hope this helps.

[WoodsWagon]

The connector and wiring about 6" back from the coolant temp sensor are known to corrode. This will cause the ECM to get a bad reading from the coolant temp sensor. If you shave off the insulation from the wire, the copper should be bright and shiny, not dull and green. The corrosion causes higher resistance in the circuit, which makes the temp sensor signal seem colder than it actually is.

[TomRhere]

For the dim lighting issue;

 

I would check the main body ground. Small gage wire coming from the battery - cable end.

Make sure there is a good clean connection where it attaches to the body.

Also clean the connections at the battery and where the negative cable is bolted to the engine block.

[derekdee]

Thanks for the help everyone. I'll connect that wiring tonite. As for the alternator, wouldn't i habe a dead battery? It starts fine, I get 12+ volts on the dash gauge upon starting. I was reading in another thread about ignition wires running to the fuses? Does the ecm channel power to these lights? Or is it straight from the fuses to the bulbs?

[zukiru]

Ecm has nothing to do with headlights. But if I pull the headlight fuse in the interior fuse box by the driver door my headlight goes dim. So check that.

[derekdee]

Isn't it odd that they all went at the same time though? It was right after I disconnected and reconnected the new ecm, hence thinking they were all related. I'll check the fuse again. I figured it was just a bulb in regards to the dash and the front headlight. Then I got pulled over for the tails. Hoping that I didn't fry any wiring, hoping its all fuse related.

[ferox]

Isn't it odd that they all went at the same time though? It was right after I disconnected and reconnected the new ecm, hence thinking they were all related.

 

Hence the suggestion to check your alternator. The idea being that your bad ECM is more likely a symptom rather than a cause. A bad regulator in the alternator may make it charge with excessive voltage. A bad rectifier in the alternator may make it charge with a percentage of AC current rather than DC. Both conditions can and will fry components and cause other electical gremlins, and you won't necessarily have a dead battery. You dash gauge should read ~14.7 volts.

[evilspawn666]

Don't know if you solved your problem with your lights since it was a month ago but you might want to check the relays. I was just having the same problem.

[derekdee]

I tore apart the casing behind the steering wheel, cut some of the vinyl casing that held the wires, traced them all, found a connection that looked faulty. Tighten up the wiring and it works now. Now I'm having issues with the Egr valve and a shake at 47 mph. Wheels are balanced, ball joints and tie rods are new... I replaced the wheel bearings a couple months ago and am wondering if I just did a poor job. I tried to wiggle the wheel, nothing. I also fixed the ujoint in the rear diff portion of the driveshaft and it broke again. Going to have to make a trip to pick and pull this week. Good luck with the wiring. Check your grounds if its not that bundle of wires.

[subynut]

Vibrations at speed can also be from a CV joint going. I have had a few CVs that still had a good boot, but would give quite the shake in the steering wheel above 30 mph.