LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

code 41 i have new ingnition module,coil and diffent opti still no fire!!!

Old Dec 21, 2003 | 02:23 PM
  #1  
97ramairtransam's Avatar
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code 41 i have new ingnition module,coil and diffent opti still no fire!!!

like title says im getting a code 41 i have absolutly no fire i have a new coil new inginition module and a differnt opti please help!!! this is on a 95 ta
Old Dec 24, 2003 | 07:38 AM
  #2  
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The PCM will set a 41 when the signal from the PCM to ICM has a problem. This signal is on the white wire of the ICM and goes to pin B and at the PCM is on the black connector pin 5. The first thing to do is disconnect both connectors and check continuity from pin B of ICM to pin 5 of the PCM connector. You may need a second wire to reach it with meter. Obviously if there is no continuity, you have a wire to fix.
This is where I believe you have the problem since you changed everything else. The alternative is the PCM Let's go a little further to rule out some other things.

If ok, connect both ends and put the meter on AC Volts. While cranking the engine, look at the signal on the white wire of the PCM. It should have between 1 and 4 volts AC on it. Remember to ground the black lead.

If no AC signal, pull the connector at the PCM (black connector) and check the signal coming out of pin 5. If there is no signal coming out of pin 5 then most likely (notice I said most likely), the PCM is bad.

If the AC signal is getting to the PCM on the white wire, you must now look at the signals from the ICM to the coil. Ignition off. Meter set to DC Volts. First check for a good ground to the ICM. Put a meter lead on the + battery terminal and probe the black wire pin C on the ICM with the other lead. It should show a full battery voltage (12 or more volts).

If not you have a bad ground.

Ignition on. Meter set to DC Volts. Now check the pink/black wire on pin A of the ICM and the white/ black wire on pin D of the ICM for battery voltage (12 or more volts) remember to ground the other lead.

If the voltage is there, the problem is the coil. If it is not on those 2 pins, you have to determine if the wire from the coil to the ICM is broken, or if the connectors are bad or the coil is bad.

Also if the voltage is not on those 2 pins, check the #11 fuse (10 amp) the supplies the ignition. If blown, no voltage either.

If the AC signal is getting to the ICM and the ICM has 12 volts on pins A and D, the ground is good to the ICM, and you still have no spark the ICM is probably bad.

Last edited by slopokrodrigez; Dec 24, 2003 at 07:42 AM.
Old Dec 24, 2003 | 09:00 AM
  #3  
Van5150's Avatar
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Try pulling Computer fuse under hood for 15 seconds.
Old Dec 25, 2003 | 04:27 AM
  #4  
Unique07's Avatar
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Originally posted by slopokrodrigez
The PCM will set a 41 when the signal from the PCM to ICM has a problem. This signal is on the white wire of the ICM and goes to pin B and at the PCM is on the black connector pin 5. The first thing to do is disconnect both connectors and check continuity from pin B of ICM to pin 5 of the PCM connector. You may need a second wire to reach it with meter. Obviously if there is no continuity, you have a wire to fix.
This is where I believe you have the problem since you changed everything else. The alternative is the PCM Let's go a little further to rule out some other things.

If ok, connect both ends and put the meter on AC Volts. While cranking the engine, look at the signal on the white wire of the PCM. It should have between 1 and 4 volts AC on it. Remember to ground the black lead.

If no AC signal, pull the connector at the PCM (black connector) and check the signal coming out of pin 5. If there is no signal coming out of pin 5 then most likely (notice I said most likely), the PCM is bad.

If the AC signal is getting to the PCM on the white wire, you must now look at the signals from the ICM to the coil. Ignition off. Meter set to DC Volts. First check for a good ground to the ICM. Put a meter lead on the + battery terminal and probe the black wire pin C on the ICM with the other lead. It should show a full battery voltage (12 or more volts).

If not you have a bad ground.

Ignition on. Meter set to DC Volts. Now check the pink/black wire on pin A of the ICM and the white/ black wire on pin D of the ICM for battery voltage (12 or more volts) remember to ground the other lead.

If the voltage is there, the problem is the coil. If it is not on those 2 pins, you have to determine if the wire from the coil to the ICM is broken, or if the connectors are bad or the coil is bad.

Also if the voltage is not on those 2 pins, check the #11 fuse (10 amp) the supplies the ignition. If blown, no voltage either.

If the AC signal is getting to the ICM and the ICM has 12 volts on pins A and D, the ground is good to the ICM, and you still have no spark the ICM is probably bad.
Now THAT'S how to reply to a post....!

Step-by-step information, flawless punctuation and paragraph breaks that makes it easy on the eyes. Nice job...hope Santa brought you the entire Swedish Bikini Model team.
Old Dec 25, 2003 | 05:05 PM
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slopokrodrigez's Avatar
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Originally posted by Unique07
Now THAT'S how to reply to a post....!

Step-by-step information, flawless punctuation and paragraph breaks that makes it easy on the eyes. Nice job...hope Santa brought you the entire Swedish Bikini Model team.
Thanks I pride myself on being good at electrical problems. Your post was a riot BTW. Hope you have a great holiday as well.

Dave
Old Dec 25, 2003 | 05:12 PM
  #6  
mickeyiz28's Avatar
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From: richmond ky
did u ever think about one of the parts you bought could be bad, cuz i bought a brand new icm back in the summer and it took me a month to figure out that i bought a bad one from napa
Old Dec 25, 2003 | 05:14 PM
  #7  
slopokrodrigez's Avatar
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Hopefully good troubleshooting techniques will determine that without "shotgunning".
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