Hello All,
I own a 87 GN with 60k and suddenly the car began to run rough last week and the Check Engine light came on. I am getting Code 34 (Cam) & 41 (MAF), so I decided to install a spare Cam & MAF sensor I had laying around. I erased the ECM memory, but I continue getting the Codes 34 & 41. I even installed a new Module thinking this would resolve the problem, but I am still getting the same codes. I checked the connections to the sensors and everything was OK. What I find weird is that I got both codes at the same time. Any suggestions will be greatly appreciated.
Mulitple codes can mean a bad ECM. Check to see if it got wet.
Phil
Phil,
Thanks for the quick reply. I have a feeling I may have a bad ECM. I'll see if my friend lends me his ECM, so I can check it out. Also, If the ECM is bad could it have damaged the CalPack & Chip too? The car runs, but when I accelerate it stutters & stumbles.
Check the grounds on the back of the head. The MAF has a dedicated ground there (and the shared one for the cam sensor is back there too).
A bad ground can cause multiple codes, since it's in the wiring harness.
Thanks Ken,
I'll check that out this morning. Would you happen to remember which head should have the ground? Passenger or Driverside rear? Also, Does anyone know where I can buy the factory service manual? If I had one I would be able to follow the engine wiring schematics and check all the grounds. Finally, Ken nice burn-out picture of your GN on your Profile.
Almost all of the wiring harness grounds are on the rear of the pass. side head. Two bolts and one of them is easiest seen from under the car.
Other grounds to check...neg. cable to the bottom of the turbo bracket, neg strap to firewall, and mounting of the coil pack to the "U" bracket.
Ken,
I did find the two bolts on the passenger side head. All the wires seemed find, but I still went ahead and removed, cleaned and reinstalled them. I erased the ECM memory, but stll 34 & 41 appear. I checked the grounds that lead to each sensor and there was a good ground to both. I also removed, cleaned and reinstalled the negative cable to turbo bracket, strap to firewall and the bolts to the coil pack bracket as you said, but they were all OK. Now I really think it is the ECM!! So later on this week I'll drive it to my friends house and swap his ECM to my car and see what happens.
I was thinking, If there wasn't a signal from the Cam sensor while the engine was cranking How is the engine running? If you unplug the Cam sensor the engine wouldn't start? The Check Engine light comes on a few seconds after the engine starts and both codes appear at the same time.
Again Ken, thanks for your help.
Be carefull before you try your friends ECM. Take a hard look at yours first. Take the curcit board out of the case. Look for rust, corrision and any burned connectors or sodier joints. Burning is caused from spiking and can blow a good ECM the minute you turn the key.
Phil
Henry,
Refer to the wiring diagrams elsewhere on this web site. Find out which terminal on both of these sensors is supposed to be ground, and check to see if it is actually grounded. I had a problem with mine. I had a motor done, and when we first started the car, I was getting a code for the MAF. Tried 3 different MAFs, and nothing helped. No ground at the sensor, even though the grounds were attached on the back of the head. The ground was broken somewhere in the harness. I ran a temporary one to the fender where I think the headlights ground, and all was well with the world. Have you done any work under the hood that may have caused movement of the harness?
The MAF ground is BLK/WHT, PNK/BLK is Ign/Ecm
The Camshaft sensor gets it's ground from the CCCI , and is the black wire. It also gets it's power directly from the CCCI, and is GRY/RED. I got all of this from the wiring page on this site. Just in case, I suggest you double check, just in case I accidentally accessed the Toyota web site or something.
Maybe the CCCI has a back connection. Have you washed your engine recently? Good Luck.
Brian
Thanks Brian & Phil,
Phil, I'll remove the ECM tonight & open it up. I'll look for any causes of a burnt ECM before plugging in my friends ECM. Good Idea!!!
Brian, Here is the story on my GN. I purchsed the car in late 90 and used it as a daily driver until early 91. I stored it in my dad's warehouse until Oct 2001, but I did start & drive the car every month. Now that I bought a home with a garage I decided to tune-up the car and bring it home. The day I decided to bring it home was when the Check Engine light came on and it began to idle & run rough. My dad did tell me that the battery was very weak on the car, so he had to put the battery booster on it. I've heard that jumping & booster can cause damages to the electrical system. I'll check the grounds again to the sensors and maybe I'll run my own ground to them. Where did you find the wiring diagrams?
Thanks Again,
Henry
Hi Henry,
Here is how to get to the wiring diagram:
Under resources, click on Technical Info
Undr Tehcnical Articles, click on Electrical, Wrining and switches
Then Click on Wiring Diagram Index
Then ECM wiring diagram.
Or:http://www.gnttype.org/techarea/images/wiring_images/ecm_turbo.jpg
Good Luck. You may want to try putting your ECM in your friends car first. Just a suggestion, but it would be a way to test your ECM, without having to worry about burning up you friends ECM. If it shows the same problems, then you would know it had something to do with the ECM, and you wouldn't have to try his.
Brian
I'll bet the battery charger zapped the ECM. Its happened to me. My battery was down and I was eager to get the car on the road, so I ran the charger on its 'high current' mode for awhile to accelerate the process. Lots of intermittent misbehavior from the ECM immediately thereafter. No amount of reseating the connectors or resetting power to it would change the behavior. Swapping for the same P/N ECM pulled from a FWD car in the junkyard cured all the problems.
By the way, there were no physical signs of damage on the ECM boards. It did run hot to the touch after the damage, however. When I discovered that, I settled on replacing it as my next move.
Hello Phil, Ken, Brian, Scott,
Here is my update!! Last night I installed my ECM in a buddies 87 GN and there were no Error Codes. His car started and ran fine with my ECM installed. I installed his ECM in my car, but as soon as the car started Codes 34 & 41 appeared again. I was looking over the ECM wiring diagram today and I believe my problem is in the wiring harness. The Cam Sensor signal is reaching the module, but the signal does not reach to the ECM. This is why the car is able to start, but once the ECM doesn't receive a signal from the module it stores code 41. As for the MAF sensor, I believe the same thing is happening. The MAF signal wire may be a broken or shorted before it reaches the ECM. Tomorrow I will use my digital voltmeter to compare the signals at the ECM plugs from the signals off the sensors. I really appreciate evryone's input into my problem and I will give everyone an update tomorrow.
Thank's,
Henry
Hello All,
Today I was able to find both of the problems with my error codes. For the Cam sensor error, I found a loose wire leading to the ECM. It seems that the previous owner had installed a switch right before the ECM connector. As for the MAF sensor, I found that the 12v supply and the ECM signal wires were in the wrong location at the MAF plug. I confirmed this by having my friend check the wire locations on his 87 GN. I have no idea how this happened? After swapping the wires to their right locations and clearing the ECM I am only getting code 34 now. I will need to purchase a new MAF, because I'm sure the MAF is toasted and this is why I'm still getting Code 34. I'll be out of town this week, so I'll install another MAF by next weekend.
Thanks,
Henry