Check Engine Light - CODE 12

93redMKII · 10-12-2009, 11:28 PM

I've got a stuck CEL with CODE 12. I've read all the forums and I can't find any broken wires (maybe I'm missing them). Car runs great, can't clear code! I've owned it for 12 years and it's been taken care of.

Here's what I've found so far, any suggestions on troubleshooting would be helpful.

- Speed sensor recently replaced by Toyota - other person had bad ground

between sensor and alternator. Could this be?

- ECU-B fuse was blown, when replaced the airbag light was on and had to

clear - this fuse supplies +12v to ECU?

- Read that distributor seal goes bad and oil leaks into distributor,

causing it to not send signal.

- Bad ground somewhere?

- Wires to injector look like they shorted out on ground. Possibly no +12v at

injector when in ON position.

- Replaced PCME (ECU) as suggested by Toyota dealer - same code.

- Wires at distributor?

- Radio drops power every now and then, becoming more frequent. Pulled and checked connections, they seem ok. This started happening before the CEL. Possibly not related, just a bad stereo.

- Replaced cap and rotor - needed to be done.

- One person had a clutch safety switch cut when alarm installed - I checked a splice in my line and replaced - no bueno (mine has factory alarm and no self-start)

- Pulled negative on battery and 2 fuses in back, as well as ECU-B fuse up front. Code won't clear.

I'm lost, and I need to pass smog for registration. The car is in great shape, but because of this light, I'm stuck! Please help!

mrjimmyx · 10-13-2009, 12:01 AM

its not the ecu fuse you pull. its the 15A fuse in the engine bay. lol.... pull it for 60 seconds. its the fuse @ the top.

93redMKII · 10-13-2009, 12:03 AM

I pulled that fuse (EFI) as well as 2 others in the posts, and the negative battery cable, all for 3 minutes. Didn't clear it.

Jason.MZW20 · 10-13-2009, 06:01 PM

That code won't clear until the problem is solved. It's a hard fault.

You need to check your distributor connector and wiring; it's on the side of the distributor, so you'll have to pull the spark plug wires. The ECU gets the NE and G signals (RPM) from the distributor. Start diagnosing there.

93redMKII · 10-13-2009, 09:12 PM

Yes I understand that. Thanks for the advice.

v vette · 10-23-2009, 08:26 PM

Quote:

Originally Posted by Jason.MZW20

That code won't clear until the problem is solved. It's a hard fault.

You need to check your distributor connector and wiring; it's on the side of the distributor, so you'll have to pull the spark plug wires. The ECU gets the NE and G signals (RPM) from the distributor. Start diagnosing there.

Yep.. I had same code and could not clear it no matter what.. I ended up getting a complete new distributor with internal guts from ebay, $95.00 delivered..The code error went away!

93redMKII · 10-24-2009, 11:18 AM

Yep, it was a broken wire in the distributor plug as I expected. I understood it would stay on until it was fixed, also.

10-12-2009, 11:28 PM	#1 (permalink)
93redMKII No Skills Join Date: Feb 2008 Location: Rohnert Park, CA Posts: 24 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (2/100% )	Check Engine Light - CODE 12 I've got a stuck CEL with CODE 12. I've read all the forums and I can't find any broken wires (maybe I'm missing them). Car runs great, can't clear code! I've owned it for 12 years and it's been taken care of. Here's what I've found so far, any suggestions on troubleshooting would be helpful. - Speed sensor recently replaced by Toyota - other person had bad ground between sensor and alternator. Could this be? - ECU-B fuse was blown, when replaced the airbag light was on and had to clear - this fuse supplies +12v to ECU? - Read that distributor seal goes bad and oil leaks into distributor, causing it to not send signal. - Bad ground somewhere? - Wires to injector look like they shorted out on ground. Possibly no +12v at injector when in ON position. - Replaced PCME (ECU) as suggested by Toyota dealer - same code. - Wires at distributor? - Radio drops power every now and then, becoming more frequent. Pulled and checked connections, they seem ok. This started happening before the CEL. Possibly not related, just a bad stereo. - Replaced cap and rotor - needed to be done. - One person had a clutch safety switch cut when alarm installed - I checked a splice in my line and replaced - no bueno (mine has factory alarm and no self-start) - Pulled negative on battery and 2 fuses in back, as well as ECU-B fuse up front. Code won't clear. I'm lost, and I need to pass smog for registration. The car is in great shape, but because of this light, I'm stuck! Please help!

10-24-2009, 11:18 AM	#7 (permalink)
93redMKII No Skills Join Date: Feb 2008 Location: Rohnert Park, CA Posts: 24 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (2/100% )	distributor Yep, it was a broken wire in the distributor plug as I expected. I understood it would stay on until it was fixed, also.

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10-13-2009, 12:01 AM	#2 (permalink)
mrjimmyx Cage Fighter Join Date: Jul 2009 Posts: 416 Thanks: 4 Thanked 12 Times in 12 Posts iTrader Rating: (1/100% )	its not the ecu fuse you pull. its the 15A fuse in the engine bay. lol.... pull it for 60 seconds. its the fuse @ the top.

10-13-2009, 12:03 AM	#3 (permalink)
93redMKII No Skills Join Date: Feb 2008 Location: Rohnert Park, CA Posts: 24 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (2/100% )	I pulled that fuse (EFI) as well as 2 others in the posts, and the negative battery cable, all for 3 minutes. Didn't clear it.

10-13-2009, 06:01 PM	#4 (permalink)
Jason.MZW20 Pig Snout Join Date: Jul 2006 Location: Victorville, CA Posts: 1,373 Thanks: 15 Thanked 111 Times in 102 Posts Blog Entries: 6 iTrader Rating: (2/100% )	That code won't clear until the problem is solved. It's a hard fault. You need to check your distributor connector and wiring; it's on the side of the distributor, so you'll have to pull the spark plug wires. The ECU gets the NE and G signals (RPM) from the distributor. Start diagnosing there.

10-13-2009, 09:12 PM	#5 (permalink)
93redMKII No Skills Join Date: Feb 2008 Location: Rohnert Park, CA Posts: 24 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (2/100% )	Yes I understand that. Thanks for the advice.