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Old 02-01-2020, 07:52 PM   #1
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1993 P30 7.4L 4L80e transmission

I have OBD-1 engine codes 12 and 43.
12-Diagnostic mode; No distributor signal to electronic control module; System PASS.
43-Electronic spark timing (EST) circuit-low voltage detected. / Electronic spark control (ESC) - circuit problems.

Could problems associated with these codes affect the transmission?

The transmission failed, was re-manufactured by Atransmissions in Michigan (has warranty), re-installed and now appears to slip under various conditions. It is full of new clean fluid.
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Old 02-02-2020, 05:09 PM   #2
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12 has a dual purpose. It's always the first code to let you know it's in diagnostic mode. If it's a hard code the engine won't run. I don't think the 43 code is related to your problem, timing is an engine parameter, it shouldn't be affected by or affect the trans, especially in OBD1.



Is the slipping a repeatable fault, can you make it happen? Are you sure it's not downshifting or the convertor is unlocking and the increase in engine RPM makes it sound like the trans is slipping? When it starts to slip if you attempt moderate acceleration does the engine RPM increase but not your speed? Does it do it any specific gear(s)?
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Old 02-02-2020, 11:19 PM   #3
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That tranny should have a limp mode...which should go into default if it cannot shift to the appropriate rpm band that the ecm requires...What you seem to be saying the tranny is trying to wander thru the gearing meaning it is shifting...A bad ground somewhere in the system can cause a lot of issues...multiple issues such as your experiencing....Or perhaps your knock sensor...they can really mess things up...so to speak...Ground issues are the probable cause..check the input to the transmission make sure its clean...

https://batauto.com/threads/g-m-%e2%...code-42.14056/
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Old 02-02-2020, 11:27 PM   #4
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That tranny should have a limp mode...which should go into default if it cannot shift to the appropriate rpm band that the ecm requires...What you see to be saying the tranny is trying to wander thru the gearing meaning it is shifting...A bad ground somewhere in the system can cause a lot of issues...multiple issues such as your experiencing....Or perhaps your knock sensor...they can really mess things up...so to speak...Ground issues are the probable cause..check the input to the transmission make sure its clean...

https://batauto.com/threads/g-m-%e2%...code-42.14056/
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Old 02-03-2020, 07:01 AM   #5
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Took it out yesterday and it is repeatable. 1st thru 3rd are smooth as silk. It pops loose in OD and 3rd. IOW it revs up and slows down. With increased pedal it slips out of 3rd and it slipped out going down hill also.
Developed another issue on yesterday's warm-up;
It did not charge up the house battery. Something else to worry about.
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Old 02-03-2020, 07:08 AM   #6
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EyezOpen, I've read some posts about the knock sensor causing similar issues, particularly with OD. I will clear the codes and check trans wiring before I drop the tranny. It is shifting and it does lock, except in OD.
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Old 02-03-2020, 08:55 AM   #7
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My P30 was shifting poorly. After finally getting a code for TPS, I replaced it and my shift problems disappeared.
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Old 02-03-2020, 11:01 AM   #8
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What is TPS?

Quote:
Originally Posted by Guzzimark View Post
My P30 was shifting poorly. After finally getting a code for TPS, I replaced it and my shift problems disappeared.

Throttle Position Sensor?
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Old 02-03-2020, 04:19 PM   #9
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Quote:
Originally Posted by Skunkape View Post
EyezOpen, I've read some posts about the knock sensor causing similar issues, particularly with OD. I will clear the codes and check trans wiring before I drop the tranny. It is shifting and it does lock, except in OD.
Check your TPS

https://www.thirdgen.org/forums/tpi/...-esc-wont.html
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Old 03-13-2020, 01:04 PM   #10
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Also check the wiring harness (external) on the side of the transmission. There should be no trans fluid. Disconnect it and check.



If there is red fluid the harness is leaking from inside the connector. Requires you dropping the pan and replacing the wire harness (not difficult).
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Old 03-14-2020, 09:09 AM   #11
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Update

It's been cold and raining a lot around here, and working on my gravel drive has been sporadic.
I was able to finally get my fat belly under it and discovered the knock sensor was removed and never reinstalled. Of course it has to come out before the starter can come out, which has to come out before the transmission. I found it in the crease of the cross member. Perfect. Makes me wonder what else that mechanic left for me to find?
There is new fluid on the pan, so I'll have to chase that down. Not sure, but it appears to be coming from the dipstick tube.
The plan for now is to install a new knock sensor (to clear the engine code) and a 124 amp alternator before I start it again. Yeah, it went bad in this mess also. Once that's done, then I'll spend some time drying off the fluid and checking for leaks on the transmission and them test drive it again.
I will keep everyone posted.
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Old 03-14-2020, 01:49 PM   #12
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You mentioned the alternator low voltage can cause all kinds of issues, it could be related
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