Bad ECU???

Hi everyone,

New to the forum and Tacoma’s , My brother bought a new car and couldn’t keep three vehicles, miami parking issues lol. So he gave me his 97 Tacoma. It’s a very nice little truck and I am very happy to have it.
It’s a 97 2.4 4x2 5 speed manual with 137k miles and he kept it very well.

The truck had issues for a while, he did a few things and so did I. It still runs very rich (smell of gas) and bogs down when you step on it.
I replaced the plugs, the wires, the distributor cap, the rotor, the fuel pump, the fuel filter and the coolant temp sensor, he had replaced the two o2 sensor and the MAF sensor. I also took out the cat converter to see if it was plugged, nothing.
Finally I took the ECU out and found some black lines under some caps like the lines are burned also the scanners don’t link to the ECU on ODB port so I am assuming the ECU is bad. What do you think?
The part number for the ECU is 89661-04240
Does the part number has to match? I am having a hard time finding a perfect match from a reputable source, I bought one from eBay and had to return it, they sent me a bad one that blows the ecu fuse.
Please help, any information would be very useful.

Thank you!
Laz

 

Ouch. That board looks to me like ike a trace burned up due to a short. Maybe repairable with a schematic and some creative soldering, but you're better off with another one.

You might be able to find the right used one through car-part.com, but first you'll need to check all the connections to the ECU to make sure nothing is shorted first. They don't burn up like that all by themselves, so there's an electrical problem elsewhere (or there was).

Is it obvious which pin the burnt trace connects to on the connector?

 

Almost looks like the electrolytic capacitors blew from the residue.

 

That’s what I think happened, in that picture I had already cleaned it a bit to see the actual damage, looked like oil from one of the caps.
I have to check if those lines go out to the plugs I didn’t think of that.
Thank you.

 

This trace burned up. I think the residue you're seeing is conformal coating.

 

Yes you are right there might be a short somewhere, and I will try car-parts thank you.

 

Yes, could be. I need to do some detective work for sure.
Thank you!

 

The small capacitor leaked out, and its actually in the area that controls the fuel injectors I am assuming as there is 4 big identical transistors in that location.
Has anybody tried a different part number for the ECU?
I called the junkyards listed in car-parts as having it in stock and they don’t have it, they already sold it.
A seller in eBay has it but the reviews are horrible, and at $400+ is not an easy gamble.
Thanks guys for any help.

 

here is a similar issue but different vehicle. the "general" information in there should apply to tacoma ECUs as well.
https://www.clublexus.com/forums/ls...s-issues-solved-ecu-leaking-capacitor-14.html

 

How’s it going everyone I know it’s a little late but I’m hoping to get an answer from this thread. I got a 97 Tacoma 2rz 2wd it’s been giving me the intermittent check engine light problem when it’s on it runs rich and when it’s off it runs perfect. Read ALOT of posts where these years give problems with the Ecm not communicating when the CEL is on. I’ve opened mine up to see the same capacitor mentioned above have a little black on the board around it. I’m wanting to know if your Ecm was the cause of it. Ecm #89661-04240 is hard to find and I’m ready to buy a plug and play from flagship 1.

 

Hi Makana808,
I have exactly the same bad capacitor as you. ECU cannot be read by OBD reader. I have the ECU repair where all the capacitors are replaced but it still will not work. My 97 Tacoma ECU is 89661-04250. Flagship1 wants $772 for that ECU which is quite a gamble because it might not work too.
Have you resolved the issue yet? Can you share your solution?

 

I have some experience with bad ecu,s generally with OBD1 early 90s Lexus, you can try Josh at Relentless Motorsports he has a reputation in the Lexus/1uzfe community for fixing ecu,s or pony up and go to flagship 1. This does sound strange though i thought Toyota had this cleared up when the OBD2 came out post 1994, i would inspect engine compartment real well for critter damage to wire harness and bad grounds.
R/
Andy

 

United Radio repairs these as well but I am unsure of the cost these days. That is a fairly un-sought after computer though, so I'd lean on just finding another at car-part.com

 

A company I worked for had a few oscilloscopes fail because of a problem with the electrolytic capacitors.
Capacitor plague - Wikipedia
My truck runs fine now, but after seeing this, I may replace the caps before a problem arises.

 

I went ahead and recapped my ECU even thou there were no signs of leakage. I used the capacitors suggested in the 1st post of the clublexus forum. Reading through the clublexus thread and watching the Car Care Nut video made me take the risk.
The result has been mostly positive. My truck before the recap would get 15-16 MPG going from home to Barstow, Ca. The route starts at sea level, climbs a few 7000ft passes and ends at about 2500ft elevation. This weekend, after the recap, the MPG was 17 going to Barstow, and 18 going home. Another positive is the low RPM, high load ping I have had since installing the S/C is gone. Before the recap I tried tuning that ping with the URD 7th injector several times. Never could get rid of the last bits of ping. Also the throttle response at freeway cruise seems better.
The big negative was the removal of the old capacitors. The ECU solder was sticky and seemed to have a high melt temperature. There were two capacitors that had large ground plane pads that were acted like heat sinks. It took too much heat and time to release the caps. Two of the support pads (not the pads that had electrical connections) delaminated and came off. As a fix I blobbed solder on the cap leads that were missing the support pads. Also hot glued the caps to the PCB for extra support. Because of this damage I may have created a latent failure and would not try recapping again.
I would consider a professional outfit with better equipment and technique. My typical offroad trip is 300 to 400 miles total, 250 miles are freeway. A solid 2-3 MPG increase is at least a $10 savings in gas per trip. A recap may pay for itself. I have a 2005 Matrix that idles rough, and MPG has dropped. Maybe I get some quotes.

 

How’s it going everyone just wanted to update. I had a problem with my 1997 2rz 2wd Tacoma ECM I took mine apart and cleaned the burnt areas under the capacitors with alcohol and it worked fine no problems until today. It gave me the same issues Ecm won’t connect and will run rich and sputter. During the time I had the first encounter with this problem I looked high and wide for a replacement Ecm for a 97 Tacoma part no. 89661-04240 and couldn’t find the exact part number so I bought a 96 Tacoma Ecm hoping it would fix the problem if it ever came up again and stored it away. Installed it today and it runs top shape! No problems at all. So if you guys are wondering if there is another ecm you could use a 96 Tacoma 2rz will work mind you it is a manual transmission so make sure donor ecm is the same. Part no. For 96 ecm is 89661-04150 worked like a charm. Only time will tell. Will keep updated if anything should come up.

 

Just wanted to add to my last reply. I believe the problem with these Ecm is humidity and moisture prior to me having this problem is I fixed my AC and it’s a must where I live 90+ degrees, I ran the AC constantly and after a few months this problem came up. After doing some research other people having this problem on rainy days maybe they run their heater cold and hot creates condensation. If you look or feel behind the glovebox where the Ecm sits there’s an air duct that runs right across in the front of the Ecm with 2 connecting points on either side, I think with these older trucks the foam seal that supposed to prevent air from leaking from the ducts get brittle and air (hot or cold) blows right into the Ecm creating moisture inside. Maybe if you seal these air ducts or somehow insulate the Ecm I think this wouldn’t be a problem. Just my 2 cents

 

Or just turn the AC on when you run the heater, depending on truck, manual or auto AC or not. I have never owned a Tacoma with auto AC so I dont know if the AC comes on automatically when in defrost or not.

 

The Tacoma's all use the ac to defog/defrost....

there is a mod to the inside of the knob to defeat this




just like I have a cover over my e-mower in my leaky metal shed...
as my taco ages......i might build a 'rain fly' over ecm......as weather extremes continue.....


or snag an extra ecm while they're still obtainable....
doesn't look like these are DIY repair.....unless experienced in silver solder

 

Except 95-97, they don't have engage the AC unless the little button is pressed there's no switch on the selector for vents, they have no idea if you select windshield or bi-level