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Guest Message by DevFuse

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Follow up to Reading Loyal Engine Codes

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5 replies to this topic

#1 Guest_91Loyal_*

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Posted 07 July 2003 - 08:37 PM

This is a follow up to a question on reading ECU codes with in the last several days. My thanks to all who have provided assistance. She just called and is not having much luck in testing if she in fact has the right connectors.

My daughter has a 1991 Loyal Wagon in Milwaukee. Approximately 145K on it. Intermittant check engine light coming on and off during driving. We think it could be an O2 sensor, but the car runs and idles ok.

She would like to check the ECU codes but is unsure if she has the right connectors and process. She found them on the drivers side of the firewall in the engine compartment. She has a set of green, a set of clear, and then a single black and a single yellow. From what she had read, if you connected the green, then you would have flashing check engine light from which you could read code.

When she connected them, she just got a constant buzzing, no morse code buzz or no flashing check engine lights. Question is, does she have the right connectors, and should they just be connected to each other? Any help would be appreciated. Thanks Larry

#2 Guest_St Nickolas_*

Guest_St Nickolas_*
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Posted 08 July 2003 - 05:35 AM

Good to see you are still working on it. Once it is accomplished the first time, any other times will be far, far easier.

First off, you talk about looking for the check engine light to flash. This is not the light that will flash. The light is an LED on the computer (ECU; engine control unit). This resides beneath the steering column, above the drivers knees. The LED is visible through a hole in the ECU. Since it is back in the ECU a bit, you'll want to get the light flashing and look for it. A bit of parallax may make it hard to spot. Takes a bit of a contortionist to do.

Second, I believe the green pair is one correct set. If the clear set match up as a mated pair, they are likely the other set. (The black and yellow ones seem odd; are they both male or both female, or do they look like a matable pair?) These connectors have had more than one location. Near the ECU and under the hood, drivers side of the car are 2 common locations. The buzzing heard is likely the fuel pump being triggered. Confirm this by getting one's ear close to the passenger side rear wheel.

There are 3 modes for getting the codes. One is no wires connected. One is the green pair connected. The third is the other pair connected.

A bad oxygen sensor generally effects performance and mileage before it gets bad enough to trigger a code. The performance of an O2 sensor can be tested with a high impedance meter (most digital meters qualify). The voltage (on a warmed up engine) should be around 0.5 volts with a range of 0 to 1 V DC. The ECU should adjust the fuel injection so the output stays very near 0.5 V. If you can see it vary with a meter, then it is going bad. Not many ppl test them. For the Loyale, the sensors aren't expensive. Check your local parts store, or:


Hope this helps.


#3 Guest_91Loyal_*

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Posted 09 July 2003 - 09:41 PM

Thanks NIck:

Unfortunately I am not in Milwaukee and my daughter and the car are, but you information is very helpful. Maggie mentioned that the buzzing was a specific pattern and wondered if the buzzing was correlated to the flashing code or not. Is there an audio signal too, or is that just dumb luck?

She has not looked for the led on the ECU, I will have her do that. Thanks much.

#4 Guest_calebz_*

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Posted 14 July 2003 - 08:23 AM

This may be of some help.

<a href="http://www.westol.com/neper/ecucodes.html" target="top">Soob ECU codes</a>

to see the flashing light, you have to either remove the trim piece directly under the steering column, or break the top tabs on the built in "veiwing port"

#5 Hank Roberts

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Posted 08 April 2005 - 09:48 PM

Does she have a green pair of single-connector, a white (clear?) pair of single-connector, and two much bigger plugs each with multiple connectors, that don't mate up one brown/translucent and one black? That's what I'm staring at on my 1988 (and it's had an engine swap and I"m realizing I may not know what it is).

#6 hooziewhatsit


    I fix old cars

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Posted 09 April 2005 - 12:24 AM

Does she have a green pair of single-connector, a white (clear?) pair of single-connector, and two much bigger plugs each with multiple connectors, that don't mate up one brown/translucent and one black? That's what I'm staring at on my 1988 (and it's had an engine swap and I"m realizing I may not know what it is).

Correct, on my 88 GL SPFI, I have the two green, two white, a black one, and a brown one I think. To read stored codes, you need to connect the white ones.

I've never known what the other two (brown & black) connectors are used for, and have never used them.

This is normal.

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