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Believe it or NOT - "Check Engine" light (CEL) demystified somewhat


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35 replies to this topic

#1 Skip

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Posted 10 February 2005 - 11:36 AM

The ECU and you

IF they are to do their job.
Our ECU's need input from electrical sensors
and control of other electrical devises.


This "job" involves making the engine run smoothly
and keeping engine pollution outputs at an acceptable level.

IF one or more of these electrical components does not present the ECU
with a resistance or output value within certain parameters it feels there is a problem.

The ECU now knows it can not do it's job properly
and therefore
alerts the driver of a problem by illuminating the CEL.

The CEL will go off - and the ECU stores the code for the problem.

The CEL is off in case another problem arises but
will relight if the first problem is not dealt with after a few start cycles.

You can retrieve these stored error codes
even if the light is off.

***However if the CEL has not illuminated
you will not have a stored error code.***

You must plug together the dark colored connectors.
These "Read Memory" connectors are black or dark brown.
Not the green connectors, (AKA "Test" connectors)
please see

Retrieval



Clearing stored codes:

If and only if you fix the problem will the error codes clear.


Disconnecting the battery will NOT repeat NOT clear these stored error codes.

The volatile memory of the ECU will retain the error codes.

To clear the stored memory codes

One must:
a) fix the electrical component so that it presents the proper output/resistance

B) clear the memory using the procedure outlined in the FSM .
please see

Error Code Clearing


I am sure this makes it all as clear
as chocolate milk.
I apologize in advance for this
incomprehensible
and lame attempt.
(batteries not included, your mileage may vary
and no warranty implied)


#2 JWX

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Posted 10 February 2005 - 12:06 PM

thank you skip

#3 scrapdaddytatum

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Posted 10 February 2005 - 01:23 PM

thanks skip

#4 bushbasher

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Posted 10 February 2005 - 01:54 PM

awesome. Never new about the CEL going off even though there might still be a problem. I figured when it goes off the problem is fixed. So my car doesnt actually just fix itself :lol:

#5 calebz

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Posted 10 February 2005 - 03:58 PM

SO can you clear the codes by simply unhooking the battery?




;)

#6 royboy159

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Posted 22 March 2005 - 10:33 PM

SO can you clear the codes by simply unhooking the battery?




;)

Hey Calebz----On newer Soobs the codes won't clear that simple. On older Soobs (EA82), after disconnecting the battery for 10 minutes, you'll be unable to retrieve any codes via the LED or MIL by the Memory Mode process. But don't worry. It won't take the ECU long to find those unrepaired problems and set new codes.:D

#7 Phaedras

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Posted 22 March 2005 - 10:54 PM

Wait...so if my CEL has turned off, yet I can still read codes from memory, there still exists a problem?

#8 grossgary

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Posted 22 March 2005 - 10:56 PM

depends when you last cleared them. they could be residual codes from weeks, months or years ago that really don't mean anything now. or they could be valid. it's best to clear them and check regularly if you suspect problems or want useful information.

#9 rallyruss

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Posted 23 March 2005 - 01:06 AM

Hey Calebz----On newer Soobs the codes won't clear that simple. On older Soobs (EA82), after disconnecting the battery for 10 minutes, you'll be unable to retrieve any codes via the LED or MIL by the Memory Mode process. But don't worry. It won't take the ECU long to find those unrepaired problems and set new codes.:D


I thinks you must have failed to detect the sarcasm in calebs comment.;)

yes this is common on most makes of cars.

good job skip. easy to understand instructions to properly troubleshoot a CEL.

#10 Skip

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Posted 23 March 2005 - 05:20 AM

Thanks Russ, most appreciated.

and thanks for pointing out it does pay to read
closely sometimes.....

I did try to lay it out in a fashion to make
reading and comprehending it easier.

The posts I see that are one big paragraph......

Do get hard to follow I believe.

#11 royboy159

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Posted 23 March 2005 - 01:34 PM

I thinks you must have failed to detect the sarcasm in calebs comment.;)

yes this is common on most makes of cars.

good job skip. easy to understand instructions to properly troubleshoot a CEL.

Hey rallyruss----There may have been sarcasm but I just wanted to clarify that you can erase stored codes in some Soobs by just disconnecting the battery.
Thanks.

#12 Ross

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Posted 23 March 2005 - 10:51 PM

A question: Should an '83 ea81t have the black connectors? If so, should they be near the green connectors or not? I cant seem to find them on mine.
Cheers.

#13 royboy159

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Posted 24 March 2005 - 01:34 PM

A question: Should an '83 ea81t have the black connectors? If so, should they be near the green connectors or not? I cant seem to find them on mine.
Cheers.

Hey Ross----The '83s may have had split connectors. One set under the driver's side of the dash, the other set at the left rear of the engine compartment. Let us know what you find.:)

#14 Ross

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Posted 26 March 2005 - 08:13 PM

Hey Ross----The '83s may have had split connectors. One set under the driver's side of the dash, the other set at the left rear of the engine compartment. Let us know what you find.:)


So since my car is right hand drive, should that be on the right side?

#15 royboy159

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Posted 26 March 2005 - 08:25 PM

So since my car is right hand drive, should that be on the right side?

Hey Ross----That's good to know next time I'm in New Zealand.:brow: I'd say under the left dash and rear left engine compartment.

#16 Ross

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Posted 26 March 2005 - 09:15 PM

I'd say under the left dash and rear left engine compartment.


Really? The computer is on the right side....

#17 naru

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Posted 26 March 2005 - 09:48 PM

A question: Should an '83 ea81t have the black connectors?
Cheers.



No.

#18 Ross

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Posted 27 March 2005 - 12:09 AM

No.


So you can't read stored codes from the ecu? or is there another way?

#19 naru

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Posted 27 March 2005 - 02:32 AM

So you can't read stored codes from the ecu? or is there another way?


Read the codes by connecting the green connectors and turning the key on w/o starting the engine.

#20 Ross

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Posted 27 March 2005 - 02:40 AM

Read the codes by connecting the green connectors and turning the key on w/o starting the engine.


Ahhh.. thanks naru, ill try that.

#21 royboy159

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Posted 27 March 2005 - 03:25 AM

Hey Ross----It's good to warm up the engine before reading codes. They will flash out on the LED of the ECU. After reading codes as per Naru, leave connectors together, take vehicle for drive with rpms exceeding 2500. When returned let engine running and check for any additional codes. Then disconnect greenies. Let us know what codes you get.;)

#22 Ross

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Posted 27 March 2005 - 07:22 PM

Ok, i took the car for a drive with the green connectors connected. After 2 or 3 mins of driving, the ECS light came on. The o2 light flashed code 24 - WOT switch remains in on or off position (at least thats what i think it said, i was dirving at the time). by the time i pulled over to check again, the code had stopped flashing (no activity on o2 light) and the ECS light had started flashing slowly. It continued to flash like this for the remainder of the drive, and i was unable to get it to repeat the code to check it.

I did check the WOT switch a while ago, and it worked, but it seemed to switch on at around half to two thirds throttle - is this normal?

Any suggestions on what the flashing ECS light means?

#23 naru

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Posted 27 March 2005 - 08:19 PM

Ok, i took the car for a drive with the green connectors connected. After 2 or 3 mins of driving, the ECS light came on. The o2 light flashed code 24 - WOT switch remains in on or off position (at least thats what i think it said, i was dirving at the time). by the time i pulled over to check again, the code had stopped flashing (no activity on o2 light) and the ECS light had started flashing slowly. It continued to flash like this for the remainder of the drive, and i was unable to get it to repeat the code to check it.

I did check the WOT switch a while ago, and it worked, but it seemed to switch on at around half to two thirds throttle - is this normal?

Any suggestions on what the flashing ECS light means?


"WOT" switch should close at 1/3 throttle not 2/3.

Flashing ECS light at this point indicates no codes.

With connectors unplugged and engine throughly warmed up,O2 sensor light should flash fairly quickly indicating proper operation.A bad sensor won`t necessarily set a code but the light is a good indicator of its condition.

#24 Ross

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Posted 27 March 2005 - 09:22 PM

I'm still unable to get stored codes from the ecs. There should definitely be some in there, but they dont show up when the green connectors are conected. What is the problem here?

#25 royboy159

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Posted 27 March 2005 - 09:42 PM

Hey Ross----After the test drive code 24 should be stored. So with the green connectors connected, the key turned to on, engine off, the LED should be flashing 24. But it's not?:-\ I'd run the engine again, disconnect a sensor to set a code, then repeat the stored code check procedure to verify that codes are being stored.:)




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