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Truck starts, idles fine, revs up fine but as soon as I put it in gear and let out the clutch it dies and check engine light comes on. I check the codes and I get 3 flashes followed by 12 flashes, repeat. Anyone know what this means?
The 3 flashes should be the ECU saying it is in the correct mode to display check engine light codes. The following 12 should be the code itself. When you say 12 flashes does it flash once, then pause, then flash twice? Or 12 total flashes? There should be a gap if 12 in total and it should read out somewhere between 11 and 80 or something like that.
Originally Posted by 95SlowRunner
Code 11 Momentary interruption in power supply to ECU (electronic control unit or computer) up to 1991
Code 12 Engine revolution signal missing
Code 13 Rpm signal to ecu missing above 1000 rpm
Code 14 Igniter signal to ecu missing
Code 16 A/T control signal missing from ecu
Code 21 Main oxygen sensor signal fault
Code 22 Water temperature sensor circuit fault
Code 23 and 24 Intake air temperature signal fault
Code 25 Air/fuel ratio LEAN
Code 26 Air/fuel ratio RICH
Code 27 Sub-oxygen sensor signal or heater circuit fault
Code 28 No.2 oxygen sensor/heater signal fault
Code 31 and 32 Air flow meter circuit or Vacuum sensor signal fault
Code 34 and 36 Turbo-charging pressure signal fault
Code 35 Altitude compensation sensor signal fault
Code 41 Throttle position circuit fault
Code 42 Vehicle speed sensor circuit
Code 43 No starter signal to the ecu
Code 51 AC signal on; DL contact off (in trany shifter with diagnostic connector jumped)
Code 52, 53 and 55 Knock sensor fault
Code 71 EGR system malfunction
Code 72 Fuel cut solenoid signal fault
Code 78 Fuel pump control signal fault
Code 81, 83, 84 and 85 TCM communication fault
This is quoted from another users post on the check engine light here.
The three is letting you know its the start of the cycle. If its giving 12 flashes straight that sounds like rpm signal missing. That comes from distributor. The service manuals are posted somewhere on this site and the toyota ones give step by step instructions on testing the circuits of the distributor. I'd recommend that before throwing a new distributor at it without checking; but the latter can't hurt unless you're short on cash.
Only other forum post I saw referencing code 12 was someone saying the ECM died and that replacing fixed it. I hope its your distributor though.
After doing some more research I came up with this, it's from an 85 service manual. This points to the 3 flashes being ignition related and the 12 flashes pointing towards the knock sensor. I'll have to inspect further. I do have another used distributor laying around. Think I'll swap it out and see if anything changes.
Interesting, thats a good find. The one I had downloaded was an 88 3vze manual. It did have the graph for 22re codes too but you never know if things were different year to year.
Knock sensor going out isn't super common but if its the original high mileage 40+ year old one it can totally age out and die. I had knock problems on my 3.0 once and it would absolutely cut ignition so you could be on the right track.
Great news! Got it fixed. Turns out the wire had come off the knock sensor, easy fix. Then the ignition signal ended up being a bad connection at the plug right before the distributor. Fixed that and no codes now. Drove it a mile or so and all is well.
More research revealed that 87 and prior use a single digit code presentation ( total number of flashes). Post 87 uses the two digit presentation (flashes for each digit place). Never knew that, learn something every day!
Thanx for the assistance, hopefully this can help someone else in the future!
IME these trucks and engines are pretty reliable, but sometimes a wire comes loose because of a service issue, or something gets chewed through by a rat. I've learned for start with the assumption all of the parts are working fine, and go looking for loose or chewed wires.
My last rat damage was they chewed through the windshield washer fluid tubing. Grr.
I feel you there, I got so fed up with ignition problems on the 89 3.0 that I rebuilt the motor wiring harness. New wires to all the plugs solved a ton of random sensor issues.
Feb 7, 2026 | 03:34 PM
