Hey all. I’ve been dealing with this code 43 service engine light for awhile and I really need some help. I’ve gone through and replaced the knock sensor and esc module. The code was pretty intermittent originally but now it kills the performance about 15 minutes into driving. From what I’ve gathered from the forums I think it’s a failure of the knock test. I’m planning on going through and checking for broken wires on the esc module and knock sensor. Does anybody have any tips on dealing with this? I have winaldl data too if that helps with any diagnosis. EDIT: also it’s worth mentioning that it likes to pop up at about 3k rpm’s once it’s warmed up.

 

https://www.thirdgen.org/forums/tbi/...code-43-a.html

 

Connect a scan tool, look at the knock counts when driving (some heavy-throttle use, too.)

As suggested, follow the service manual procedure for diagnosing and repairing that code.

 

I’ve followed the path on the gm service guide and it hasn’t done anything for m besides telling me that the code is intermittent and it’s likely a poor connector somewhere. All wires look good for continuity and the ground is reading good as well. The only unusual thing to me is that ckt 439, pink and black wire, is also reading as grounded. I’m not sure if it’s because it’s a short to ground or if that reading is normal. Any advice?

 

OK, this may NOT have any bearing on your issue, because you do not have a corvette. However if you have an issue with the ECS circuit, you are looking for a voltage with key ON, engine off. In a corvette, you are back probing ckt439 at the ECM white connector to ESC ckt486 for 9volts.If you have less than 9vdc on that ckt you have an open in ignition, above 9vdc you have a short to ground. You want to look at that circuit again to ensure you are probing it correctly. Again, not sure if the 3rd gen is exactly the same or not. GL though...

 

I tested that connection from ecm to esc and got 12v. I tested with the negative connected to negative terminal on the battery and again with it connected to the ground on the esc connecter. The positive on my multimeter was in the pink and black wire running from ckt 439 at the ecm. I’m not sure what it’s supposed to read on our third gens but that’s what I got. If anybody knows what voltage it should be reading or where I might be able to find out it would be much appreciated.

 

B7 of the ecm 9.2-9.3v

 

Thanks @Tuned Performance Is that chart out of the Firebird service manual and if so what page?

 

It’s from factory manual 89-92 tbi , found online so I don’t know what page

 

Good info, GL on the issue.

 

In my 1988 Firebird factory service manual, that is in 6E2, Section A - 5.0L (VIN E) Driveability & Emissions (appears in the upper right corner as page 6E2-A-6.

 

I’ve tried everything in the gm service manual and from what I can see the wires are showing good voltage but it’s still doing the same thing. I’m dropping it off at a shop tonight that supposedly does good work on gms/Pontiac so hopefully they’re able to diagnose it. I’ll let y’all know what they say.

 

If all the wiring checks out, no shorts or opens, then a new ECM may be in your future.

 

Update: well I feel like an idiot. He went through and noticed that one of the spark plug wires was damaged where I couldn’t see it. He replaced it and it runs great now. Night and day difference. I never even thought to check them. Thanks for the advice everyone

 

How does a damaged plug wire cause a Code 43?