Scanner code wizards help me please
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,112
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From: San Antonio Texas
Scanner code wizards help me please
96 LT4
I just did another Opti replacement and just got everything buttoned up to see if it would run or if I really screwed it up. I say,"screwed it up" because when the Opti went bad, I was out in the middle of West Texas with NO communications. The car would run, but just barely. I had no choice but to drive it sputtering, misfiring and puking gas out the exhaust, till I could get cell service and call for a flatbed to get me back home.
Back to today: got everything back together and plugged in my code scanner just to watch while I fired it up. Started it up and it runs, but the check engine light is on. (Smokes, but I expected some because it flooded the exhaust with gas it was running so rich when the Opti went sour.) My code scanner says," P1641 Malfunction Indicator Lamp (MIL) Control Circuit" Well DUH, the light is on but it doesn't tell me why! I do have the Service manuals for this car, but I can't find anything yet.(I guess I don't know how to use these books correctly yet.) Haven't got a clue where to start on a P1641 cause I don't know exactly what it means.
Any help later would be appreciated. Got to stop for today and meet my Son this afternoon, but will be back in town later tonight to check on this. TIA.
I just did another Opti replacement and just got everything buttoned up to see if it would run or if I really screwed it up. I say,"screwed it up" because when the Opti went bad, I was out in the middle of West Texas with NO communications. The car would run, but just barely. I had no choice but to drive it sputtering, misfiring and puking gas out the exhaust, till I could get cell service and call for a flatbed to get me back home.
Back to today: got everything back together and plugged in my code scanner just to watch while I fired it up. Started it up and it runs, but the check engine light is on. (Smokes, but I expected some because it flooded the exhaust with gas it was running so rich when the Opti went sour.) My code scanner says," P1641 Malfunction Indicator Lamp (MIL) Control Circuit" Well DUH, the light is on but it doesn't tell me why! I do have the Service manuals for this car, but I can't find anything yet.(I guess I don't know how to use these books correctly yet.) Haven't got a clue where to start on a P1641 cause I don't know exactly what it means.
Any help later would be appreciated. Got to stop for today and meet my Son this afternoon, but will be back in town later tonight to check on this. TIA.
Team Owner
Joined: Sep 2003
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The 1641 seems to be FAN CONTROL and the later FSM format changed a little but if you check the index in section 6 I believe it should take you to the appropriate section of the FSM for diagnostics. Did you try the scanner before replacing the OPTI OR just replaced it because of the run situation?
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,112
Likes: 117
From: San Antonio Texas
I had the scanner with me when the Opti went bad. Suspected it was the Opti and hooked up the scanner and it read multiple misfires on all cylinders.
The Fan Ckt. makes sense because I have an Electric water pump that I run from a relay energized by the fan relay (PINK WIRE). It has been wired like that for a few years so I know that part works fine. But...While I had everything down, I rigged up a switch to run the water pump with the engine off, so I could burp air out of the system and run a little coolant through the engine after shut off too. Looked at my wiring and it looks like I have an incompatable 'back feed' through that pink wire when I flip my pump run switch. Looked at my fan run ckt. and sure enough the 5A fuse was blown. Guess I'll have to reconfigure my engine off waterpump ckt. with another relay or a diode to keep from feeding back into that pink wire for the fan run ckt.
The Fan Ckt. makes sense because I have an Electric water pump that I run from a relay energized by the fan relay (PINK WIRE). It has been wired like that for a few years so I know that part works fine. But...While I had everything down, I rigged up a switch to run the water pump with the engine off, so I could burp air out of the system and run a little coolant through the engine after shut off too. Looked at my wiring and it looks like I have an incompatable 'back feed' through that pink wire when I flip my pump run switch. Looked at my fan run ckt. and sure enough the 5A fuse was blown. Guess I'll have to reconfigure my engine off waterpump ckt. with another relay or a diode to keep from feeding back into that pink wire for the fan run ckt.
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,112
Likes: 117
From: San Antonio Texas
Thanks for the tip, you were dead on !
Team Owner
Joined: Dec 2012
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From: Outside the Quick Stop N.J.
While I was under hood I unplugged and checked the temp sensor plug and harness. I really don't think the plug was making a good connection. I've got some tiny tools so I stuck a little file in the plug holes and gave them a little cleaning then tightening and cleaned the prongs on the sensor. Rewrapped the sensor pigtail and plugged it in. Turned the key and started it up with my scanner plugged in. Car started and ran MUCH smoother and threw no codes. I think I had an intermittent temp sensor connection that was contributing to my problems.
Thanks for the tip, you were dead on !
Thanks for the tip, you were dead on !
