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Codes 12, 23, 42, 52 pulled over night

Tue Feb 18, 2014 12:48 am

Car: 91 ST185 w/ST205 swap

Ok so yesterday I changed plugs, did an oil change, and changed my battery. I continued to drive the car for the rest of the day without any issues. This morning I went to drive it and it fell flat on its face at 3k rpm in 1st gear and continued to do so. I'm guessing this is the limp mode system yes? So despite that...I had my CEL flash on and off 1 time which brought up the codes 12, 23, 42, 52. Would any of you like to share how you would plan the attack on these? I think they are:

RPM Signal
Intake Air Temp Sensor
Vehicle Speed Sensor
Knock Sensor Signal
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Re: Codes 12, 23, 42, 52 pulled over night

Tue Feb 18, 2014 5:14 pm

That's a lot of codes to get all at once. Check all your electrical plugs and ground connections first.

You will want to focus on code 12 - that one pretty much says that the ECU can't tell where the engine is in its rotation...

Does the motor still idle and run ok-ish below 3k rpm?

-Charlie

Re: Codes 12, 23, 42, 52 pulled over night

Tue Feb 18, 2014 9:07 pm

Those are pretty random codes to have together.
You might want to check the wiring where you moved it, if you have a swap. You might have disturbed some crappy connections. If the wiring is good you might want to clear the codes and see if they come back.
You can also jump TE2 [yes, TE2, not TE1] and E1 and put the ECU into a more sensetive diagnostic mode [won't work for a 90/91 ECU, only for 92^].

Re: Codes 12, 23, 42, 52 pulled over night

Wed Feb 19, 2014 1:16 am

First off I'd check the alternator belt and the alternator connections, the really rough running can be caused by that as well.

Re: Codes 12, 23, 42, 52 pulled over night

Wed Feb 19, 2014 4:16 am

phattyduck wrote:That's a lot of codes to get all at once. Check all your electrical plugs and ground connections first.

You will want to focus on code 12 - that one pretty much says that the ECU can't tell where the engine is in its rotation...

Does the motor still idle and run ok-ish below 3k rpm?

-Charlie


The morning it pulled the codes (it was cold) It took longer than usual to start but once it did it idled perfect and ran 100% till it hit 3k then started stalling on me, So I limped it back home and parked it. It starts fine and idles fine. Do you think the alternator would have something to do with this as stated above? The alternator looks like the original one and the motor has approx 65k-70k miles on it.

Re: Codes 12, 23, 42, 52 pulled over night

Wed Feb 19, 2014 6:06 am

When I forgot to tighten the alt belt it started and idled like a champ but as soon as I drove it and made it do any kind of work (ie shortly past letting the clutch out) it would bog and run like garbage. The lack of power supplied to the systems from either alternator issues or ground/connection issues like Charlie mentioned are the most likely ways to get a whole pile of seemingly unrelated errors all coming from measurements, since power/ground issues will cause the readings to be way out to lunch.

Re: Codes 12, 23, 42, 52 pulled over night

Wed Feb 19, 2014 1:45 pm

underscore wrote:When I forgot to tighten the alt belt it started and idled like a champ but as soon as I drove it and made it do any kind of work (ie shortly past letting the clutch out) it would bog and run like garbage. The lack of power supplied to the systems from either alternator issues or ground/connection issues like Charlie mentioned are the most likely ways to get a whole pile of seemingly unrelated errors all coming from measurements, since power/ground issues will cause the readings to be way out to lunch.


The tension on my alt. belt is good, and I was able to drive the car smoothly till about 3000 rpm before it started to hiccup. I'll check multiple grounds and see how those are. I drove the car everyday with no issue until now. The only thing I changed before all this were the plugs (BKR7EIX) and the oil (10w40). I'm pretty puzzled.

Re: Codes 12, 23, 42, 52 pulled over night

Wed Feb 19, 2014 4:53 pm

How long did you drive the car for? I found in the past that when the power has been off the ecu for a while the ecu has to relearn where idle is. You can get around this by adjusting the idle control screw higher to say 900rpm and then put back down to 700rpm later

Re: Codes 12, 23, 42, 52 pulled over night

Thu Feb 20, 2014 1:21 am

The previous owner only put 5k on it in 4 years. When I bought it I had to change batteries because his was drained completely. I drove it about 40mi from his house to mine...It sat for a few days...I drove it consistently for 2 days after then it started all this.

Re: Codes 12, 23, 42, 52 pulled over night

Thu Feb 20, 2014 1:22 am

DeeCee wrote:How long did you drive the car for? I found in the past that when the power has been off the ecu for a while the ecu has to relearn where idle is. You can get around this by adjusting the idle control screw higher to say 900rpm and then put back down to 700rpm later


The previous owner only put 5k on it in 4 years. When I bought it I had to change batteries because his was drained completely. I drove it about 40mi from his house to mine...It sat for a few days...I drove it consistently for 2 days after then it started all this.

Re: Codes 12, 23, 42, 52 pulled over night

Thu Feb 20, 2014 4:37 am

If it sat for that long the belt might be good but the alt could be dead, take it to a parts store and get it tested if you can.

Re: Codes 12, 23, 42, 52 pulled over night

Sat Feb 22, 2014 9:17 pm

Just went through similar running issue with mine, code 12 was the main issue. ended up finding the wires to the dizzy on the vehicle side to be broken (had just a few strands left hanging on to stay running but missed like hell above 3000). anyways hope that helps. good luck

Re: Codes 12, 23, 42, 52 pulled over night

Sun Feb 23, 2014 7:38 pm

DTE wrote:Just went through similar running issue with mine, code 12 was the main issue. ended up finding the wires to the dizzy on the vehicle side to be broken (had just a few strands left hanging on to stay running but missed like hell above 3000). anyways hope that helps. good luck


Thank you! I just ordered OE wires because I was noticing the magnecor's that are currently on it are pretty worn and some times pop off the plug. Lets hope it works. Thanks for your input.

Re: Codes 12, 23, 42, 52 pulled over night

Sat Jul 22, 2017 11:42 pm

Hey guys I'm stuck on the side of the road, I have diagnosed code 12... HELP!!!!
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