Corona (3SF-E) DTC 12 - Toyota Nation Forum : Toyota Car and Truck Forums

razirafi · 03-25-2011, 04:09 AM

Hi to all, I would like to ask for help from anyone who has experienced this problem and found a way to fix it. This particular vehicle that I am servicing puts out an error code 12 (missing RPM signal) but the tachometer is functioning and the engine runs fine except for intermittent misfiring at idle. I checked the NE, G, IGF, and IGT signals and wiring according to the service manual and they are OK. I even re-wired these signal lines but the problem stays the same. With regards to the misfiring, I think the high tension leads need to be replaced. I swapped the distributor and igniter with another one but the problem still persists. I have noticed that at idle the check engine light comes on but when I rev it to about 1000 RPM the check engine light goes off. When I release the accelerator and the engine goes back to idle the check engine light comes on again. I can reproduce this symptom everytime I rev the engine and then back down to idle. Code 12 everytime. Does anyone have any clue to this problem?

CoronaST170 · 08-30-2011, 12:50 AM

Hi, The igniter and the distributor unit would have been my first guess.. You seem to have checked all common parts for the problem but its still there.. if you are revving it to 1000rpm then...

I would check the MAP sensor and injectors, I think when you are revving it there is more pressure been drawn in and the MAP sensor sees that and add the right amount of petrol and then your engine light goes off

You can also check spark plugs to see if its running good and oxygen sensor..

let me know how things go

Marc

razirafi · 08-30-2011, 07:05 AM

Thank you for your insights. Actually the problem was solved by replacing the high tension wires with a new set. The vehicle has been idling very smoothly after the replacement.

CoronaST170 · 08-30-2011, 08:14 PM

Awesome, Glad you have got it fixed... You feel much happier now

razirafi · 08-31-2011, 05:25 AM

Yes, I was happy indeed. Two days after my first post, I was able to nail down that problem so I did not bother to check on my post until you posted a reply. I really appreciate your taking the time to post your troubleshooting hints and I am sure that the community will find it useful sometime. Thanks again.