1993 SW2 Engine Codes 41 & 42
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Junior Member
Joined: Oct 2024
Posts: 12
1993 SW2 Engine Codes 41 & 42
My 1993 SW2 is throwing intermittent codes 41 and 42 together. My shop manual indicates these are PCM and Electronic Ignition Control module possible shorts or ground wire problems or possibly the modules themselves are going bad? The engine died once on me when stopped at an intersection traffic light, But started up again and kept running safely. I haven't been driving much until I get this figured out. Rather than try to trouble shoot electrical, should I just replace the PCM and EIC modules? They total around $450.00 for both.
I understand you can buy refurbished PCMs and they program it for you with your VIN etc. Are these then straight plug and play ? Or do they need further programming ?
I've owned the car since new and it has 438,000 miles on the chassis and interior. I had another engine swapped in when the oil pump failed at 375,000 miles. I want to keep her running.
Thanks for any advice !
-Marty
I understand you can buy refurbished PCMs and they program it for you with your VIN etc. Are these then straight plug and play ? Or do they need further programming ?
I've owned the car since new and it has 438,000 miles on the chassis and interior. I had another engine swapped in when the oil pump failed at 375,000 miles. I want to keep her running.
Thanks for any advice !
-Marty
Super Moderator
Joined: Jul 2005
Posts: 12,387
From: Slightly off center
Interesting.
https://batauto.com/threads/g-m-%E2%...code-42.14056/
This last post indicates that the injectors are failing and that the spark chip in the ignition module is burning up trying to compensate. I have no idea as to the validity of this statement, but it is something to consider.
I have attached schematics from the '95 FSM as well as a Chilton 91 to 93 book. I've used the wiring diagrams all the way up through 97 and 499% of the vehicle they are the same. I did not take the time to check and see if they are identical.
The blur on the Chilton's pictures is unavoidable because the ink has diffused outward on the cheap paper it's on. My cell phone has a 40 megapixel camera on it so that's about as good as it's going to get and you can blow it up and still read it.
The full page shots are probably not readable which is why I took segments after that as well.
Per Gary, you definitely want to inspect all of the ground splice packs in the vehicle. With a 31 year old vehicle, there's bound to be corrosion. It only takes one of those grounds to get lifted for the current to find the next easiest path to flow. And depending where that goes, it's amazing the weird ****e that will go on.
Ultimately, I would check all the grounds first, then the wiring between the PCM and ICM / DIS.
There are all kinds of handoffs of the ignition timing control back and forth between the PCM and the ICM depending on various conditions that are for our purposes not necessary to explore but there are explanations out there. Many of the handoffs are triggered when the ignition system encounters problems doing its job and hands control back to the PCM which runs on the base timing programmed into the PCM instead of advancing the timing based on map and other things.
Anyway, if none of this fixes your issue, I would look into a set of rebuilt fuel injectors. They are easy to swap out and I don't think terribly expensive.
Do not get the ultra cheap set as the rebuild has been demonstrated to be complete ****.
-------
Note that the explanation involving the fuel injector replacement did not come from troubleshooting a Saturn, it came from troubleshooting the Chevy in the late '80s on an OBD1 gm fuel injected car..
You've had this vehicle long enough to know how to properly maintain it and I suspect you also have the gift of analytical reasoning and have mechanically and electrically maintained it during this time as well.
Continue to troubleshoot logically and you will solve this.
PLEASE stop back in and periodically update us, especially with the solution. I can't find a documented solution on a Saturn anywhere.
Thank you
Derf
https://batauto.com/threads/g-m-%E2%...code-42.14056/
This last post indicates that the injectors are failing and that the spark chip in the ignition module is burning up trying to compensate. I have no idea as to the validity of this statement, but it is something to consider.
I have attached schematics from the '95 FSM as well as a Chilton 91 to 93 book. I've used the wiring diagrams all the way up through 97 and 499% of the vehicle they are the same. I did not take the time to check and see if they are identical.
The blur on the Chilton's pictures is unavoidable because the ink has diffused outward on the cheap paper it's on. My cell phone has a 40 megapixel camera on it so that's about as good as it's going to get and you can blow it up and still read it.
The full page shots are probably not readable which is why I took segments after that as well.
Per Gary, you definitely want to inspect all of the ground splice packs in the vehicle. With a 31 year old vehicle, there's bound to be corrosion. It only takes one of those grounds to get lifted for the current to find the next easiest path to flow. And depending where that goes, it's amazing the weird ****e that will go on.
Ultimately, I would check all the grounds first, then the wiring between the PCM and ICM / DIS.
There are all kinds of handoffs of the ignition timing control back and forth between the PCM and the ICM depending on various conditions that are for our purposes not necessary to explore but there are explanations out there. Many of the handoffs are triggered when the ignition system encounters problems doing its job and hands control back to the PCM which runs on the base timing programmed into the PCM instead of advancing the timing based on map and other things.
Anyway, if none of this fixes your issue, I would look into a set of rebuilt fuel injectors. They are easy to swap out and I don't think terribly expensive.
Do not get the ultra cheap set as the rebuild has been demonstrated to be complete ****.
-------
Note that the explanation involving the fuel injector replacement did not come from troubleshooting a Saturn, it came from troubleshooting the Chevy in the late '80s on an OBD1 gm fuel injected car..
You've had this vehicle long enough to know how to properly maintain it and I suspect you also have the gift of analytical reasoning and have mechanically and electrically maintained it during this time as well.
Continue to troubleshoot logically and you will solve this.
PLEASE stop back in and periodically update us, especially with the solution. I can't find a documented solution on a Saturn anywhere.
Thank you
Derf
Thread Starter
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Junior Member
Joined: Oct 2024
Posts: 12
Derf,
Thank you very much for the photos from the manuals and the advice. I will continue to try to diagnose it. The last two times I've driven it, about five miles each, it did not trigger the check engine light.
-Marty
Thank you very much for the photos from the manuals and the advice. I will continue to try to diagnose it. The last two times I've driven it, about five miles each, it did not trigger the check engine light.
-Marty
Senior Member
Joined: Jul 2011
Posts: 5,557
From: Anniston, AL
Did you do any work on it between the last time you posted and now? That seems kind of odd. And congratulations for keeping it going for so many miles. I'm impressed! And derf will tell you that's not an easy thing to do. LOL
Thread Starter
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Junior Member
Joined: Oct 2024
Posts: 12
Rube,
I did check the electrical connectors at the plug wires / injector block, making sure they were tight but did not disconnect them and plug them back in. I understand you should disconnect the battery before doing that, correct ? I have a Chilton's and full three volume shop manual from Saturn.
I may take her on a longer drive and see if I get the check engine light again. If so I can check codes with my jumper wire on the OBD 1.
One more symptom that might be related ...usually the car starts immediately after turning the ignition key. The last few months there is often a lag of a second or so before the starter engages after turning the key, then it starts right up as usual. I know the battery is good.
Thanks ! -Marty
I did check the electrical connectors at the plug wires / injector block, making sure they were tight but did not disconnect them and plug them back in. I understand you should disconnect the battery before doing that, correct ? I have a Chilton's and full three volume shop manual from Saturn.
I may take her on a longer drive and see if I get the check engine light again. If so I can check codes with my jumper wire on the OBD 1.
One more symptom that might be related ...usually the car starts immediately after turning the ignition key. The last few months there is often a lag of a second or so before the starter engages after turning the key, then it starts right up as usual. I know the battery is good.
Thanks ! -Marty
Senior Member
Joined: Jan 2024
Posts: 630
From: Davison, MI
Operation CHARM: Car repair manuals for everyone.
Home >> Saturn >> 1993 >> SW L4-1.9L DOHC VIN 7 >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> Related Tests, Information and Procedures >> Chart 1 On-Board Diagnostic System Check
DESCRIPTION
The diagnostic circuit check is always the starting point for any malfunction code or driveability problem. This check verifies the PCM's on board diagnostics are functioning properly. While performing a diagnostic circuit check, record codes and flags for use in diagnosing possible sub-system failures.
OPERATION
Key, "ON" - Engine "OFF" SES telltale should be "ON" steady.
When ALDL connector Pin B is grounded to Pin A with Key "ON" - Engine "OFF" diagnostic mode is entered.
^ Code 12 will flash the SES indicating diagnostic communication.
^ Code 12 will flash three times followed by any other Engine Codes (EC) that may be stored.
^ If code 12 is not indicated, a problem is present within the diagnostic system itself.
^ Code 11 will be displayed LAST to indicate if there are any Transmission Codes (TC) stored in memory. The TC codes will flash on the "SHIFT TO D2" lamp or the "HOT" lamp.
NOTE: Do not operate the vehicle for a prolonged period of time in this mode. Damage to the Catalytic Converter may result.
DIAGNOSTIC AIDS
The following circuits are energized when the vehicle enters diagnostic mode:
^ Cooling fan is turned "ON".
^ IACV is pulsed in and out.
^ EVO is cycled.
^ CCP is cycled "ON".
^ EGR is cycled "ON".
^ Hot telltale turned "ON".
pro multis · About Operation CHARM
Home >> Saturn >> 1993 >> SW L4-1.9L DOHC VIN 7 >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> Related Tests, Information and Procedures >> Chart 1 On-Board Diagnostic System Check
Chart 1 On-Board Diagnostic System Check
Chart I.:
PCM Wiring:
Scan Tool Hookup To ALDL Connector.:
DESCRIPTION
The diagnostic circuit check is always the starting point for any malfunction code or driveability problem. This check verifies the PCM's on board diagnostics are functioning properly. While performing a diagnostic circuit check, record codes and flags for use in diagnosing possible sub-system failures.
OPERATION
Key, "ON" - Engine "OFF" SES telltale should be "ON" steady.
When ALDL connector Pin B is grounded to Pin A with Key "ON" - Engine "OFF" diagnostic mode is entered.
^ Code 12 will flash the SES indicating diagnostic communication.
^ Code 12 will flash three times followed by any other Engine Codes (EC) that may be stored.
^ If code 12 is not indicated, a problem is present within the diagnostic system itself.
^ Code 11 will be displayed LAST to indicate if there are any Transmission Codes (TC) stored in memory. The TC codes will flash on the "SHIFT TO D2" lamp or the "HOT" lamp.
NOTE: Do not operate the vehicle for a prolonged period of time in this mode. Damage to the Catalytic Converter may result.
DIAGNOSTIC AIDS
The following circuits are energized when the vehicle enters diagnostic mode:
^ Cooling fan is turned "ON".
^ IACV is pulsed in and out.
^ EVO is cycled.
^ CCP is cycled "ON".
^ EGR is cycled "ON".
^ Hot telltale turned "ON".
pro multis · About Operation CHARM
