SYS flashing

[Demps]

My next step would be to disconnect battery negative terminal, reseat PROM (if piggyback...make sure secure), and reconnect battery.

Ted

[Hib Halverson]

Originally Posted by petervankleeck

Without the engine running, when I put the key in the ignition the SYS flashes on the dash. Starts right up, flashing the SYS, strongly runs for an undetermined amount of time and stalls. Throws the C41 code. New fuel pumps and fuel relays. Could the key chip be the problem? Just installed the Haibeck AYBKG chip. Resolved all kinds of issues (idle is perfect; runs cooler; and all this time I thought the high idle was a missed vacuum leak) but this SYS persists. It's not the ECM. Runs like a champ, when it's running. Any help would be appreciated.

Thanks!

Peter

1990 ZR1 #659

Service engine light is off but SYS is flashing and, using CCM diagnostics, you see C41 which means CCM code 41 is current. CCM code 41 is a serial data circuit loss of communications. To solve that you really need the FSM and a DVM.

Now, if the service engine light has been on, maybe you have an ECM code 41 which is a cylinder select fault. Try removing the ECM calibration, cleaning the pins and sockets with contact cleaner then reseating the chip.

1 to 4 light on with key-on/engine-off indicates a possible ECM problem or a short to ground in ckt 956.

Because you have all this stuff happening at once, not only would I clean and reseat the PROM, but I'd clean and reseat all four ECM connectors.

[DRM500RUBYZR-1]

Ted and hib above are correct for next steps.
However, you should check a couple of other things as a continuation of your battery and Alternator test.
1- was the battery load tested?
2- Remove both cables form the battery.
3- Clean the cable ends after removing the bolts.
4- Inspect the bolts, or preferably replace them.
5- While cables are DISCONNECTED, inspect the positive where it goes to the junction block, making sure that it is tight and clean.
6- Re-connect all, insert key.

Still SYS ?

If yes, now follow Ted's and Hibs advice.
The fact that you see SYS before starting still points to an electrical power issue, OR the connection to the ECM the 4 connectors, or the prom, or a pinched wire from the ECM.
The fact that you are getting a code indicates a comm failure, at least to some extent.
If these things do not resolve it, Hib is correct.
Pour a beverage, and sit quietly and read through the diagnostic procedure for this in the Factory Service Manual.

Have you experienced any other "odd" occurrences, either electrical or performance?
Keep us posted as you have!
Marty

[petervankleeck]

Thanks, Gentlemen, for the replies.

Disconnected the negative and pulled the prom. Everything was very clean. After reassembling, all the codes were clear and I drove the car all afternoon in N VA traffic without incident. It ran so well in all kinds of traffic conditions I was beginning to think all was well.

After it sat for about three hours, I went out for a grocery run and the SYS was back on. I noticed the low battery light also comes on when the code occurs.

When I pull the prom, and replace it, I have never driven the car long enough to see if it will finally fail. It starts and runs great. Only after it sits does the problem reoccur.

My service manual is already hog-eared and well worn.

Time to check the myriad of connections.

Thanks again!

Peter

[Paul Workman]

Scattered system faults often is due to ground issues. Grounding hasn't been discussed, but you'd want to eliminate grounds as a contributor, especially due to the intermittent nature of the problem.

Refer to the FSM, but there are two gang ground points having several circuits each grounded under the lugs at the back of the engine, under the MAP module. I used a wire brush and contact cleaner followed up with a thin coating of dielectric grease to ward off moisture.

Also... Have you had the ECM scanned for codes? One of the best $100 I ever spent was on an AutoXray scanner. They're no longer made, but that thing has saved me countless hours of troubleshooting on the several vehicles in my driveway over the years. (I keep it in the glove box for quick access and real time monitoring.)

Anyway, a scanner is a powerful tool. See if and auto parts store has an OBD-I capable scanner and see what gives. And, if I may throw in a suggestion, your symptoms are pretty close to how my Jeep acted when the crank position sensor failed, including the SYS light. Just a thought and something to "ear mark" for investigation in your quest.

Intermittent electrical problems can test the patience of a saint. But, hang in there. Sooner or later the problem will show up when you can check stuff out.

Good luck. Keep us posted!

[Jagdpanzer]

Peter,
You are welcome to barrow my Tech 1A scan tool if you want.


Sent from my iPhone using ZR-1 Net Registry

[petervankleeck]

Paul, the first problem I had with the car in the Spring of 2016 was a cracked barrel on the crankshaft sensor. Interesting you mentioned that in your post.

Time has not allowed me to pursue the issue in earnest. To have such a knowledgeable resource as the members of this forum offer is truly remarkable and greatly appreciated.

Phil, if I can’t resolve this issue before the October meeting, I may take you up on your offer to borrow your scan tool.

Many thanks for all the help.

Peter

[petervankleeck]

Gentlemen,

I have hesitated to say I have sorted out the issue and the car is running reliably, but I think I figured out the problem. I was sure the alternator and battery were good, which they were. The problem was with old, starting to rust and for the negative side, loose/stripped battery terminal connections. I popped the two out, replaced the cables with new terminal connectors, and (big surprise) the code problem and stalling stopped.

Ultimately it was what you said it would be. Fortunately, the problem was not further down the line.

Thanks again for the help!

Peter #649