Code 42 revisited

[Subfixer]

As discussed in an old thread, I get random detonation, followed by the SES light, secondaries are inhibited. Code 43 comes up as the problem. No other codes are set.

I had previously installed a new knock sensor which did not solve the problem. All checks in the FSM are good. Car is stock except for Mark's chip. Problem is present with or without Mark's chip.

While working on a radiator swap, I figured I would pull the plenum and have another look at this problem.

I found the secondary vacuum valve was leaking by, so I put in a good one, and installed a new vacuum check valve also.

I checked the ignition module for bent pins, but found none.

Any clue as to where I should check next before I button this up?
I do have a spare used Ignition module if I need it.

Thanks

[Ccmano]

I’m aware of one instance where the electrical connectors of the plug at the rear of the DIS (the ones the pins go in to) were opened too large causing an intermittent connection. At least that was presumed to be the case as the code stayed away for good after they were tightened.

The other thing that can happen at that plug is the pins go in next to the connector rather than through it. Once again causing an intermittent connection.
H
:cheers:

[lfalzarano]

How about the O2 sensors in front of the CATs? O2 sensors effect the adjustments to the ECU. The oxygen sensor relays information based on the ratio of the fuel to air being delivered into the cylinders via a sensing element. Faulty knock sensors can allow increased pre-ignition noises, misfires, backfires, and rough or jerky acceleration.

Just a guess and another place to look.


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[Subfixer]

I forgot to mention that I replaced both O2 sensors after the knock sensor replacement didn't fix the problem.

It seems that the knock sensor hears the detonation, but the timing does not retard.
I've checked all the wiring and grounds to/from the ECU and the DIS and to the O2 sensors and knock sensor. All ring out OK.

Everything is pointing to the ECU and I don't have a spare.....

[lfalzarano]

Is the chip firmly clicking into place in the ECU? I’ve heard that it can come loose causing this issue and other squirrelly issues.

If you are still having issues, You could also send the ECU to Jerry or Marc for testing.


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[Jax ZR1]

Have you had any luck getting this fixed, my car is doing the same thing and I have not been able to figure it out, any help would be great. Thanks

[Subfixer]

I replaced the DIS module under the plenum and it seems to be better.
Only had an SES once since replacement.

I'm not convinced this is the final fix.

[G8nightman]

The knock sensor board on a 92 is on the ecm chip. I replaced mine fixed the issue.


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[Subfixer]

SES showed up again once yesterday and twice today.
First two times after a warm start.
Third time after running about 5 minutes.
All three times just normal in town cruising, no full throttle.
No codes stored......

[Subfixer]

Ok, got some codes today...

Code 43 is back, with Code 66(I had the switch in the "power" position when the SES light came on).
Reseated Prom again.
Is the knock circuit on the prom or on that other little circuit board next to the prom?
I'm using Mark's piggyback prom, but I have this issue with the stock prom also.
Mark's prom bypasses the original programmed chip, but still uses the circuit adjacent to the programmed chip.
Original post:
http://zr1.net/forum/showthread.php?t=30890

[G8nightman]

its on the prom Mark piggyback dose not have anything to do with the knock circuit board

[Ccmano]

On a 90 (not sure about 91) the knock sensor logic is contained in a separate module Located on the passenger side panel below the coolant fill tank. It looks like this. It?s mounted on the outside with easy access.
I have three new ones for sale if you need one.
H
:cheers:
https://farm66.staticflickr.com/65535/48762107118_e5b418cd6b_c.jpg (https://flic.kr/p/2hhWxAN)

[G8nightman]

On a 90 (not sure about 91) the knock sensor logic is contained in a separate module Located on the passenger side panel below the coolant fill tank. It looks like this. It?s mounted on the outside with easy access.

I have three new ones for sale if you need one.

H

:cheers:

https://farm66.staticflickr.com/65535/48762107118_e5b418cd6b_c.jpg (https://flic.kr/p/2hhWxAN)



Yea that?s on a 90 only


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[Subfixer]

I took G8nightman's advice and replaced the MEM-CAL (Jerry has some). Talking to Mark H., I was educated that the Knock Sensor circuitry is part of the 91-95 MEM-CAL (its the little white circuit board and I think the 2 chips below it), replacing the separate unit the 90's use.
No SES for 4 days now, so I'm cautiously optimistic.

[G8nightman]

Cool glad it got resolved. I was going crazy with the same issue when I first got my 91 z.


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