Not Out of Woods Yet. Intermittent Comm ECM Loss?

That or that ground connection coming and going certainly didn’t help.

 

yeah thatt
underside is the 1st 5 pix(bronze color)
i didnt see anything on tht side

i agree with your comment about the ground that was 'eventually found and repaired'
this on/off/on/off/on bc of that corroded connection, could of caused dmg

 

united radio said they could look at ECM but cannot guar that they could fix

upfix replied that they need a 'repair request' with pix and explanation of what are symptoms of truck
(this is exactly what i did.....so i dont know what they are asking for)
maybe a punt

 

Looks a bit crusty. But the intermittent part has me skeptical.
@Dm93 might give his opinion. I don't deal with internals much.

 

TN
WAAAAY intermittent b4 i found and replaced the corroded ground wire

now
after 10m drive, CE lite comes on and stays on(and hot AC blowing)
no codes to be read
scan tool screen goes blank

after 1hr or 2, the truck starts and runs....no codes....and cold AC...scan tool reads data

so i say intermittent (prob better adjective)
CE comes on and must limp home.......then starts all over again after 1hr of so of sitting

appreciate your comments as always!!!!!!!

 

Certainly sound like something isn't happy once it gets warm?

The big clue here is that the the CE light comes on.
Are you saying that the scan tool can NOT communicate with the ECM when this happens?

 

yes^^^

 

Only thing I know to do would be check pins 4 & 5 on the DLC for ground.
And pin 16 for Power.

I'd suspect you have other issues if any of these were missing.
Unless your scan tool just uses chassis ground. Then "maybe" you could have a a no com if the CG was bad?
But not likely.

 

assuming plug ecm back in and connect battery then test.......correct?

 

I can tell you that in the 50+ years in the tech industry, electrolytic capacitors have been responsible for multiple of equipment/network problems. If you have the tools and expertise to replace the C120 33mfd electrolytic, I would give it a try. Key is correct tools, temp controlled soldiering iron, soldier wick, to remove old soldier, fine rosin core soldier, and patience. Be sure to watch the polarity when installing the new capacitor. Good luck either way.

 

The power and grounds at the DLC are not dependent on the ECM being in the truck.
So no, the ECM doesn't have to be in the truck.
But you kind of need the truck to be in limp mode to check it.
If I were a betting man, I'd bet you wont find an issue when checking those pins.
But it doesn't cost anything to check either.
Only reason I mention it is because you had a previous Ground issue.

Again, not likely to find the issue by checking.
But I'd check the pins and and inspect ground point mounts while I was at it.
EB and ID

 

bc of the skill/tools needed to perform AND my lack of experience
Will be 1)sending off 2)buy a RM unit with warranty

I saw one vid that the technician used 3 different soldering irons for specific part

It’s just above my pay grade
Don’t want to risk a rookie F-up

 

TN

EB is 100% good

going check ID point next

another update
Welder neighbor knows electronic board repair friend….lives 10miles away
Going to go there for his opinion (not to fix….but to confirm if rectangle box’s feet and under capacitor are normal)

 

Keep us updated.
Be pretty cool if you can fix this on your own.
Not too many guy can/could DIY it.

 

Just my .02 cents but multilayer PCB'S when you put a soldering iron to them it can have bad results.

 

The Toyota ECMs from the 90s seem to be getting quite problematic as they get older, from what I've been seeing on here it seems quite common with the early 1st gen ECMs that they either won't communicate at all or communicate intermittently and/or have various random drivability issues.

Some part number ECMs are also quite expensive to repair/replace, I know one person had a 97 3.4L 4x4 manual (89661-04310) and it was $1800 to repair.

 

Ouch^^^

I saw UpFix/flagship have RM’d ones in stock (luckily mine is automatic)
$400-$600 89661-04160

im up to 90% sure ECM is issue
Still going to take to neighbor’s friends electronic repair guy’s house just for inspection to confirm that is burnt

thanks for comments/advice

 

What about the contacts on your ignition switch

mine would run fine cold........then after 30min AM2 branch would start heating up

then run wonky.....and eventually blow the am2 fuse

went thru this for about 4 months........till it would only run 5min and blow

lubing the cylinder is a bbad ideal, switch sits right under it....especially graphite

switch and cylinder should be replaced after 150K

makes me wonder if some of you are still running underwear and socks from 30yrs ago....yuk


I replaced the cylinder years earlier.......the switch never crossed my mind


Only about 1 out of 20 does it end up being ecm that's sure its it

 

Man OS
I thought the same thing
(About the ECM being the issue on these 1st gens)

no way ECM
Dealership way of charging owners just to cover all the bases kinda thing

maybe Karma for me thinking that
But once I found tht 2018 thread where 2 others had exact same symptoms
(Limp mode w/CE light/ac blows hot/scan tool screen goes blank)
And then total normalcy after 2hrs…….

Bumped me up from 10% to 60% this cause is ECM

Now bc of others comments of the board condition, I’m up to 90%

 

I have started to think along these routes with my 95. As the only time I can even pull codes is with engine running and moving and even then readings are flakey. Today tells me tps, o2s, iat and maf. Shut down engine and rechecked ( did not clear anything or disconnect bat) but engine was off and got 0 codes send error, Restarted and drove and got 02’s again. Both 02’s were replaced a couple weeks ago with walker cat and denso sensors. Then tried to clear codes with hard shut down( disconnected battery and cables wired together .) still instant cel.
so could the switch cause this? I do notice at times that I have to play with the key to get steering to unlock?