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GM OBD codes 42 and 43

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Bluecollerboater

Contributing Member
I have recently replaced my long block with a remanned by Jasper. I have had other posts asking about problems on the original block. The engine is a 1994 Volvo Penta Gipmda. I cant get it to run evenly enough to set the timing. I am getting code 42 (electronic spark timing) and code 43(electronic spark control). I believe the code 43 is because of the knock sensor, it is rusted and not looking happy. I am going to replace it in spring time. I think the code 42 means that the ignition control module also has to be replaced? I would also like to know if there is a way to test my pickup coil? If anyone has any ideas on anything else to check i would appreciate any help on this matter.Thanks.
 
The 43 could be due to a bad connection (rusty) at the knock sensor.

The 42 means an unexpected voltage at the IC or BYPASS signals (wiring between distributor and ECM)...could be a corroded pin or one not seated well inside the connector.

If the engine isn't "run(ning) evenly enough to set the timing", then you may want to check the basics - sound plug wires and their connections are correct and compression, especially if the engine has behaved like this since it was assembled....
 
The knock sensor is all rusted and I believe the casing is broken. It definitely needs to be replaced. I will check all the connections between the distributor and the ECM, especially the pins. Thanks for the heads up.

Does anyone know how to test the pickup coil in the distributor ?
 
I don"t know jack about modern systems, but I'd make sure the plug wires were on the proper plugs before I did anything else.
 
pickup coil - test for ~ 800 ohms (+/- 100 ohms) between the two leads. if ok, check for either lead being shorted to ground. if ok, not the pickup coil.
 
Ok. Update boat still at shop. I have replaced the knock sensor. I replaced the map sensor( I got a code 33 so I put the old one back on) and I sent the computer to OBD Diagnostics to be tested( passed they said it was fine and they cleared the 42 and 43 code). I have replaced the control module in the distributor as well. My mechanic says all he is getting now is tps code and it won't idle correctly, he replaced it and it still won't idle right. I am thinking maybe the map sensor I have( the old one) is bad and the new map sensor I returned was correct and the vacuum is to low and it is setting off the tps code. He is going to try and replace the throttle body gaskets next.

The boat is at the mechanic who replaced my long blocks shop. I am starting to think he is just telling me what I want to hear. He has switched out parts with supposedly known good ones. And nothing has worked yet. When I brought it back It was because it did not idle well. It's a Jasper long block and the warranty is up at the beginning of next summer. I have not had the boat in the water yet because it is not running correctly. I am starting to think I just blew $5000! Any ideas what this might be would be greatly appreciated.
 
So the tps code set after the 42 and 43 were present?

Checking the tps and wiring is straight forward....the tps is nothing more than a resistor connected to the throttle thats informs the computer how much it is open.

as far as the idle instability...have you put a vacuum gauge on it?
 
This boat has been back to the mechanic several times. I did put a vacuum gauge on it about a month ago and it was unstable at idle but low like 16 to 18 inches. at 1000 rpm it was at i think 20 to 22 inches.And ran great. i brought it back for the unstable idle and the mechanic cut the vacuum hose from the map sensor to the back of the throttle body in half, blocking off the half that went to the back of the throttle body and leaving the half that went to the map sensor open. It did idle very well like that. But i told him this was not correct.

The boat is still at the mechanic now. So I cant check anything at the moment.
 
vacuum numbers indicate the mechanical parts are in decent shape...

having the MAP sensor exposed to the atmosphere, vs the intake manifold, is wrong...instead of cutting the hose, he could have removed the connector and inserted a jumper...i'd be inclined to find another "mechanic"... and one that understands the older GM systems..

have you had independent verification the plug wires are in the correct order and are securely fastened at both ends...and that each plug fires?
 
Makomark,
I realize this was wrong. I know the mechanicals of the engine are in good shape. I did a compression test, vacuum test and checked the fuel pressure and they were all good. I know the plug wires are routed correctly from when i did the compression check. I know they are seated at both ends. I have not checked to see if all plugs were firing with a timing light but all plugs are blackish and wet like its running rich. The computerized tbi is kicking my butt. it will run great a 1000 rpm but at idle it stalls.

Needless to say. I will be picking up the boat on my next day off.
Why would it idle great with the map sensor disconnected and the back of the throttle body plugged?
Am I looking for a vacuum leak or something else?

Any suggestions on what to check next would be greatly appreciated.
 
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sounds somewhat counterintuitive to me...exposing the MAP to the atmosphere would be telling the computer you went to WOT...that said, it would contrdict the TPS, assuming it was functioning correctly...with a TPS code set, I'd have to research how the computer would prioritize its inputs.

That said, if the plugs are wet and black, and the code in the computer is correct (fuel map matches the engine), I'd suspect the injectors are leaking and inducing the rich state...with an elevated idle, I'd guess that the engine can consume the fuel and keep running...with a normal idle rpm and the rich state, the engine stalls...just my gut feelings there.

If it turns out to be injectors, they have been "orphaned" by the OEM and you aren't likely to find any new ones...I'd suggest finding a local shop that can rebuild them....some have found aftermarket units at NAPA but I can't recall any part numbers...It may be wise to have the shop just rebuil the entire injector body...again, just my two cents...
 
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