ECM troubleshooting

[vilant]

Thought I'd ask for the collective's help on this.
So, I'll start from the beginning, provide the symptoms, what I've done to correct, and where I'm at.
So it started over a year ago, I would get an intermittent Code 31 on the ECM (cam sensor missing or too many pulses). So I ordered a new cam sensor and replaced the old one.
Problem persists but doesn't occur as often. So, I clean up all ground connections to frame and bell housing. Problem still persists.
It was mentioned that the ECM may be bad and when rebuilt it will go away. But first it is recommended to replace the battery, as the battery absorbs a lot of electrical noise, and if it's on it's way out, it may be the culprit (plus it's cheaper than a new ECM). Replace battery, problem still persists but happens even a little less often.
So, I finally bit the bullet and sent my ECM for repair. My ECM tested bad and was previously reconditioned. The future is looking dark. Jerry lent me his personal, spare ECM. I hook it up and when I turn key to "run" the radiator fan immediately comes on (which is weird because it never did that before) when I "start" the car, it turns over, is idling really high, the "service engine soon" light comes on, and I see "SYS" flashing on LCD. So, I turn the car off and go into diagnostic mode. I now have a Code 41 on the CCM (loss of ECM serial data communications). WTF!!
So I go to the diagnostic tree of Code 41 and start following the procedure



I do as directed. Tear apart the interior to access the CCM (really f***ing fun let me tell you) to test connection between WC13 and B15. I get an open.
Now," how the hell did that happen" I'm thinking. My ECM worked except for the Code 31 issue. How did I lose it?
P.S. side note. Follow the diagnostic tree above, notice "If problem is not located, see Diagostics Aids on facing page. Here's a pic



Pretty funny...TBD???
Anyway, that's where I'm at. I did a little digging on Solutions and I found Tccrab's issue where the ECM pins where bad and that was causing his gremlins. So now I'm thinking maybe bad pin connectors. I keep on looking on Solutions and I see the '90 pin diagram. here's the link
http://www.zr1.net/forum/showpost.ph...8&postcount=10

Notice how B15 and B20 are listed as not used, yet the diagnostic tree I have, has me testing those very same pins for continuity. I checked, there's no wires connected there. Again WTF!!! No wonder I have no continuity. The diagnostic tree and facing diagram show B15 & B20 as the serial data connection, yet there's no wires connected (please don't say it works wirelessly, lol).
Can someone look at their FSM and tell me if the Code 41 CCM procedure is the same? Or snap a picture for me. I want to A) make sure my FSM is correct, and B) to check continuity on the serial data line to make sure I have a good connection. If I do, then my CCM is probably bad too
Any thoughts or ideas are greatly welcomed and appreciated.
Thanks, Joe

[G8nightman]

ECM troubles Suck I'm going through similar issue but with a code 43 Knock sensor. I replaced it still code is still there. I disconnected the batt to clear the codes now I'm getting a code 44 lean My FSM code 41 is wrong Mem cal (chip)

[Marc Haibeck]

Hi Joe,

If the cooling fans turn on before the engine is started, the program in the ECM is not running and the ECM is in backup mode. The most common cause in your situation is that the calibration chip is not plugged in to the ECM.

The CCM will flag a serial data error if there is no data from the ECM (program not running) or if the data is in the wrong format. The serial data format may be wrong if there is a chip in the ECM but it is the incorrect model year for the car.

[vilant]

Originally Posted by G8nightman

ECM troubles Suck I'm going through similar issue but with a code 43 Knock sensor. I replaced it still code is still there. I disconnected the batt to clear the codes now I'm getting a code 44 lean My FSM code 41 is wrong Mem cal (chip)

Did you have your ECM tested to see if it was bad? If it is, hopefully it wasn't reconditioned before and all it needs is a reflow (I heard that's how the boards are reconditioned, not sure if they actually change out any components, e.g. resistors, caps, IC's). I assume you have the '91 FSM not the '90, right?

[vilant]

Originally Posted by Marc Haibeck

Hi Joe,

If the cooling fans turn on before the engine is started, the program in the ECM is not running and the ECM is in backup mode. The most common cause in your situation is that the calibration chip is not plugged in to the ECM.

The CCM will flag a serial data error if there is no data from the ECM (program not running) or if the data is in the wrong format. The serial data format may be wrong if there is a chip in the ECM but it is the incorrect model year for the car.

One of the first things I did was reseat all the connectors and the chip. Same result. The chip I used in the spare ECM was the one I pulled from my personal one before I sent it out . That's why I asked you before if possibly my chips could be corrupted (unlikely I agree, but not out of the realm of possiblities). I was originally thinking it's either 1)comm line between the ECM and CCM is not good (either the pins at the connector or the actual wire) 2) bad CCM 3) corrupted chips.
I do have your chip that I haven't installed yet, I could test with that and see what happens. What would happen putting in without the ported plenum and injector housing? Car would run rich?
I can also try reseating the chips on the holder too (I've seen instances in electronics where a little bit of corrosion forms on the chip legs. Sometimes reseating fixes it or if it's bad, some very fine sandpaper will do the trick). I'll dig around to see where the comm line goes to. I'm just worried my FSM is not accurate. I've noticed minor discrepancies in mine compared to other 1990 FSM's (Like B15 not being used).

[vilant]

OK figured out part of my problem. If you look in the diagnostic tree it says to test B15 in the blue connector. Well first off, there is no blue connector, but each connector is stamped with a letter A=yellow B=red C=green D=brown. So, I was testing red (B) connector 15. Just looked through supplemental schematics book. They have connections listed by color, e.g. Y15 would be yellow connector #15. The serial data line is B15 (brown connector) in the supplemental, otherwise known as D15. The editor should be fired

[G8nightman]

Originally Posted by vilant

Did you have your ECM tested to see if it was bad? If it is, hopefully it wasn't reconditioned before and all it needs is a reflow (I heard that's how the boards are reconditioned, not sure if they actually change out any components, e.g. resistors, caps, IC's). I assume you have the '91 FSM not the '90, right?

yes its a 91 FSM. I think I'm going to send my ECM to jerry for a referb.

[Marc Haibeck]

Hi Joe,

If you have a good chip plugged in with the correct orientation and the cooling fans turn on when the ignition is turned on but the engine is not started, the ECM is basically dead. It will run the engine in backup mode but it will not communicate on the serial data line.

A top end ported engine will run about 5% lean for fuel if an OE chip is used. However that's at 50% load or more. The car can be driven safely with porting, headers and a stock chip if the car is driven gently.