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symptoms of dead or dying ecu / ecm - 1984 ea81t


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88 replies to this topic

#51 naru

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Posted 14 October 2013 - 11:43 AM

I think it will run if you repair the CTS issue.

 

83 ECMs are 46089 7110,84s are 46089 7210 or 7320.



#52 lastchance

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Posted 14 October 2013 - 01:05 PM

I think it will run if you repair the CTS issue.

 

83 ECMs are 46089 7110,84s are 46089 7210 or 7320.

 

i'll work on it when i get home...

 

checking the resistance on the CTS should be done ??? 

 

i got the ECS light for the coolant temp sensor and atmospheric pressure sensor, i see on the pinout you posted position #3 is the "coolant thermosensor", is that different than the coolant temp sensor? if it's the same i can put one lead on this pin and the other on the plug for the CTS itself to check (accurately) for resistance, right? 



#53 naru

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Posted 14 October 2013 - 01:45 PM

Yes,#3.

Leads like you said to check the harness.(cts unplugged)

Leave the second lead on negative to check sensor and harness together(cts plugged in).

Sensor itself should be several thousand ohms cold,.2-3k at 70 degrees F..Higher colder.12k max.

 

Likely a corroded connection at the CTS.



#54 lastchance

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Posted 14 October 2013 - 02:39 PM

Yes,#3.

Leads like you said to check the harness.(cts unplugged)

Leave the second lead on negative to check sensor and harness together(cts plugged in).

Sensor itself should be several thousand ohms cold,.2-3k at 70 degrees F..Higher colder.12k max.

 

Likely a corroded connection at the CTS.

 

got it, thanks man.

 

the CTS is the single prong on the left of the engine, near/on the thermostat housing, right? the AAV is the connector that plugs right into the top of housing, but the CTS is different and NOT on the radiator like some confuse it to be. haha!



#55 naru

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Posted 14 October 2013 - 05:19 PM

CTS is the double prong one in nearly the same location.

Single prong one is for the gauge.



#56 lastchance

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Posted 15 October 2013 - 06:25 PM

upon inspection i noticed the CTS had been replaced at one time or another with a newer looking plug-type jobby, the pigtail was spliced into the original wiring... this is what it looks like: http://images.whisys...e/B62/36413.jpg

 

is that what the factory CTS looks like for an ea81t? 

 

near the CTS i noticed the single prong for the gauge, it looks like this, right? https://www.rockauto...559-0&width=450



#57 naru

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Posted 15 October 2013 - 09:24 PM

Yes and yes.



#58 lastchance

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Posted 16 October 2013 - 06:27 PM

i was suspecting some issues with the air flow meter, checked resistance on each of the five pins in accordance with the ECU pinout - everything checks out there, i'm getting good at this! hahahaaha

 

i checked resistance on the CTS, it's fine but i forgot to check while running. i noticed the back/bottom of the plug was cracked/missing so some grime/dirt got up in there - most likely the cause for a dirt connection. didn't see any corrosion but made sure to clean up the plug and business end of the CTS as best i could. 

 

i'll do the resistance check on the CTS tomorrow to see what it's at cold and warm, like naru mentioned.

 

both of the ECMs i have share the same part number, i double checked today... so it's still super strange that the car won't start/run with the other ECM.



#59 ivans imports

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Posted 17 October 2013 - 09:41 AM

ecm # still have two kicken



#60 lastchance

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Posted 18 October 2013 - 08:26 AM

ecm # still have two kicken

thanks man, i have a line on a few but will let you know.

 

in turbo wagon news...

 

i tested the CTS for resistance while cold, also while warm, again after driving around the block - i found that it didn't change (stayed low, around 30-42 ohms, no hundreds or thousands, just 30-42), i was testing by putting one lead to battery - and the other backprobing the CTS pigtail/harness. 

 

what does that mean, having really low resistance across the CTS, rather than changing or variable at higher resistance? 



#61 naru

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Posted 18 October 2013 - 10:34 AM

CTS is NFG or harness is shorted.

Take another reading across the unplugged CTS.



#62 lastchance

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Posted 18 October 2013 - 10:40 AM

CTS is NFG or harness is shorted.

Take another reading across the unplugged CTS.

 

got it.

 

test the same way while unplugged? lead to negative battery, other to prongs inside unplugged CTS on the harness end, right? 

 

i searched this morning for an ea81t CTS and could only find that single spade one, will an ea82t CTS work in my car? are the resistance range(s) the same? 



#63 naru

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Posted 18 October 2013 - 10:59 AM

Both leads on the unplugged CTS.

EA-82T CTS is identical AFAIK.



#64 lastchance

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Posted 18 October 2013 - 11:23 AM

Both leads on the unplugged CTS.

EA-82T CTS is identical AFAIK.

 

both leads on unplugged CTS while cold and again while warm to verify the CTS is operating correctly at varying engine temps, correct? 



#65 naru

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Posted 18 October 2013 - 11:31 AM

If the reading is way off,I would not bother w/different temps.



#66 lastchance

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Posted 18 October 2013 - 11:59 AM

If the reading is way off,I would not bother w/different temps.

 got it, i'll report back.



#67 lastchance

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Posted 18 October 2013 - 05:31 PM

Both leads on the unplugged CTS.

EA-82T CTS is identical AFAIK.

 

with my multimeter on the lowest setting (200) i was getting a reading of 0.4 doing this test... 

 

sounds like a fried CTS to me and the reason i'm getting that trouble code. 



#68 lastchance

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Posted 05 November 2013 - 02:12 PM

i replaced the CTS, code went away. sweet.

 

i still have code 41 - atmosphere pressure sensor or circuit

 

is that an integrated piece of the ECM or a sensor elsewhere? 

 

i'm still getting the symptoms of missing/running rich when the car is warm. 



#69 naru

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Posted 05 November 2013 - 08:00 PM

Integrated into the ECU for 84s.
Stand alone for 83s.

84 FSM diagnosis for code 41 is "replace the ECU".
I would try disconnecting altitude signal connector near the round knock box plug in case a faulty knock box is some how responsible.
Doubt this code is responsible for your running symptoms.

#70 lastchance

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Posted 05 November 2013 - 09:55 PM

Integrated into the ECU for 84s.
Stand alone for 83s.

84 FSM diagnosis for code 41 is "replace the ECU".
I would try disconnecting altitude signal connector near the round knock box plug in case a faulty knock box is some how responsible.
Doubt this code is responsible for your running symptoms.

 

round knock box plug? is that one of two right above the air flow meter in the engine bay? those are the only two round plugs i can think of.

 

i'm beginning to think my issues are mechanical since i've diagnosed almost all of the trouble code issues over the last few months.

 

do you think a compression check is in order? 



#71 ArtRat007

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Posted 05 November 2013 - 10:02 PM

sorry didnt read whole thread but did you vacuum check? that will tell you alot more than compression test



#72 lastchance

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Posted 05 November 2013 - 10:32 PM

Vacuum check? You mean for leaks, right?

I just did the other day and was pretty convinced that was part of my issue... I sprayed starter fluid around all the vacuum connections (while running, on a cold engine) and didn't notice any real changes in idle.

It definitely starts strong, idles perfect when cold but once the engine temp starts to come up it runs really poor.

#73 ArtRat007

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Posted 06 November 2013 - 01:20 AM

no i mean if you get a vacuum gauge and securely attach it to your intake manifold it should read 20 lbs. of pressure evenly the whole time the egine is running on all cylinders :lol: and you should be relieved



#74 lastchance

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Posted 06 November 2013 - 09:55 AM

no i mean if you get a vacuum gauge and securely attach it to your intake manifold it should read 20 lbs. of pressure evenly the whole time the egine is running on all cylinders :lol: and you should be relieved

 

got it.

 

i should be connecting the vacuum gauge to somewhere on the intake manifold, right? 



#75 naru

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Posted 06 November 2013 - 01:04 PM

 

round knock box plug? is that one of two right above the air flow meter in the engine bay? those are the only two round plugs i can think of.
 
i'm beginning to think my issues are mechanical since i've diagnosed almost all of the trouble code issues over the last few months.
 
do you think a compression check is in order?

No,it is on the other side by the coil.Altitude connector is seperate.You are supposed to disconnect it w/setting timing so that it does not interfere.

Compression,vacuum and fuel pressure checks are all good ideas.

Miss at hot idle sounds most likely like an unmetered air or vacuum leak, though.
I would try injecting some propane into the intake.If the idle smoothes,you can eliminate mechanical problems.

Carefully inspect the large rubber intake tube and all associated plumbing for cracks or leaks.
PCV hoses too.
I had to add a few clamps.




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