94 Es300 P1600 Problem

[MS1500]

I have a 1994 ES300 that the engine light came on. I took it to my local machanic and he couldnt pull any codes off of it. I took it to another location and they came up with a code of P1600 "Electronic Control Module Battery" I was wondering if there is an internal battery in the ECM or if it is something else. I am also haveing trouble finding the ECM, I was told it was in the engine compartment but I do not see it. My car also has a few other problems and I am wondering if they can be caused by a faulty ECM.

1. While driving the engine RPM's will jump up and drop intermitintly even when maintaining speed.

2. The gas guage does not read the correct amount. The amount will be off vering amounts.

Any information would help.

[lexis lexus]

ecm is located under the glove compartment, not too difficult to get there. The real problem is finding a replacement. I believe, the ecm draws a small electrical current from the (main car) battery, as it will maintain trip meter data, codes etc. Disconnecting that battery clears the codes and trip meter data.

You have to get the ECM out, snap a pix of the lable w/ the numbers, then start looking for replacement, new about $700, yanker yard $25, ebay around $100-$200, and you can get yours refurbed via several on line sites for about $150. I have an old one from my '94 that had another problem and may have a good battery in it, and one I picked up at a junk yard, but they may not be a match. Let me know.

Not sure if this prob will cause your other difficulties, but fix it anyway and see.

LL

[MS1500]

I went to the Lexus dealer today and they said that it was eather the wire suppling 12v to the ECM when the car is off or it is the ECM. The apraisal to fix it was around $1300. I took the car home and decided to check if the wire was bad. I ran a wire from the ECM to the battery. I pulled the plug out to find the hot wire, I put it back, hooked up the wire and turned on the car. To my supprise the check engine light was not on. I disconected the wire and turned on the car again and the check engine light was still off. I drove the car and stoped and started the car a few times and the check enging light didn't come back on. I can only think that the plug was loose or makeing pore contact. As an added bonus the dash lights that were out started working again. If the light comes back on I will let you know.