lj78 code 12

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F

flyfishbc

10 Year 15 Year
Joined
Apr 25, 2010
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23
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88
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bc canada
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still have code twelve, PLEEEAAASE help. i have changed fuel filter, changed crank position sensor, and checked for continuity in all wires from crank sensor and timer control valve to the ecu, everything seems fine. injector pump is brand new , less than 6000k on it. i reset ecu and light stays out for about 5 minutes then comes back on. i have no power, there are 2 other trucks in town and the can do 60k at the bottom of the hill and be doing 90k at the top. i do 90k at the bottom and 60k at the top. i don't know what else to do. :bang:
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I have done a quick scan on google. Is the pump correctly timed to the engine?
Is the cambelt timing correct. As a few posts suggest it is a timing issue if all the other parts are o.k.
Cam belt could be one tooth out?
Also one forum suggested coolant temp sensor..... 2lte surf timer control valve problems - ToyotaDiesel.com

Will keep an eye out
 
removed timer control valve and cleaned. there was a little junk in there. and checked temp sensor, i think the right one? light still comes on. can i tell if the timing is right with a timing light, or do i have to remove cover to check?
 
The main temp sensor is the one towards the rear 1/3 of the block under the intake manifold. Usually green in colour.

~John
 
i found out that the previous owner sold me this rig over the whole code 12 thing. he did put in a brand new injector pump. therefore it shouldn't be pump related, tcv etc. i have checked everything else on the code 12 list. i'm at a lost what to do next. how do i check the timing, for the belt jumping a tooth? i can't see this being the problem, as the previous owner had the code, then change the pump but code remains. i would hope the timing wouldn't be wrong with both pumps, and it was the toyota dealer that changed the pump. is there another pump in the tank that could be screwed, or should i drop the tank, clean it and change the line to the filter. if it is blocked would the internal pump pressure be wrong, thus triggering a code 12. HELP ME PLEASE the previous owner is on the forum as killerv asking many of the same questions i have asked
 
I personally have never had to deal with this particular fault.
However start with the basics and check every setting as if you have rebuilt the motor.
(had to do this for a friends Petrol motor, and found the dizzy was 180 deg out)

Use the factory manual and.....
Check valve / cam belt timing.
Check pump alignment / timing.
Check EGR valve.
Check TPS.
Check all sensors.
Check Turbo system
Check ECU (remove and open cover looking for damaged resistors and Caps)

As suggested by some forum posts on other groups the fault may be caused by another system.
Which is infuencing the good sytem into a fault condition.

Sorry cant be of any more assistance.
 
I had a similar issue. i changed the pump too.
It was wiring all along.
Remove the glove box and take the protective black sheath from the wires going to the CPU.
While the vehicle is running, try to wiggle/push/pull with the sensor wires. see how the vehicle reacts and the engine light.
I had to tuck the wire loom in a specific position towards the top left of the space at the back so the wires were in the correct position.
Aafter that no engine light and turbo light works.
 
ok, now i have checked timing marks on cam, crank, and injectoer pump. they are all lined up perfectly. changed main temp sensor, checked my timing. timing is 21' at idle. i don't have base line to compare to though. does anyone know what my timing should be. 21 sounds a little high. and 16 at about 1500 rpm. set the tps to .66v, my rpm at idle went from 700ish too 1100ish. should i leave tps there and turn down idle on pump? still code 12 light. i don't know how much hair i have left to pull out.
 
Sorry to hear finding the fault is proving hard.
I would put the TPS back where it was and leave it be if idle was all good...Before tweek.
ECU uses TPS position to control engine...It doesn't even need to be on the engine!
Have you taken a look inside the ECU.
The caps can fail and spew over the board. And can give all sorts of faults before the truck wont even run.
 
It has to be wiring or ECU related.

I got myself a new pump just because of this issue and still had the code.
Lived with for a while until i tucked the wire bundle correctly at the back of the dash.
While the vehicle is running, wiggle the individual sensor wires, tush/tug on them a bit to see, if there is any change. It was the case with me.

I still have the cold starting issues,
I opened up my ECU yesterday to check it out. It looked fine to me. so i closed it up and reinstalled. vehicle was running fine next morning and took it to work and back.

What i have read, quite a few toyota ECUs develop faulty capacitors. Mine looked fine, but i am thinking about changing mine.
After new pumps sensors and wiring, only ECU is left to modify.

Open the ECU and check for caps for leakage,bulging and resistors for burning etc.

Another way to try to get codes is when driving the vehicle, maybe that can give you a lead.

2.4LTE Fault Codes

We can get it sorted out.
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i looked at the ecu. it looks ok. i will look again though. i have been thinking about just getting another one to try out. then redoing all the caps in the one i have, then i know they r all good. i just adjusted the idle at the throttle plate and left the tps where we moved it to. idle is still a little high, but power seems a little better. the check engine light was on when i went for a drive, then went out for about a minute, and came back on. first time i have seen it off since getting the truck. just wish it had stayed that way. appreciate all the help from forum readers, apparently i still need a little more. does no one know what my timing should be at idle.
 
Sorry, i donot know how to measure timing in degrees etc. i just line up the marks. I guess i have to do some reading online.
The light going on a off shows that the ECU is getting inconsistent readings/values.
Did you try wiggling the wires with the engine running?
 
Giggling the wiring harness behind the glove compartment WORKED! No more code 12! No more check engine light! The light still works, in case you are wondering. What a blessing to find this website. The nagging light that has never gone dark is now history.

I know it's probably only confirmation bias, but it seems like I managed to advance the ignition at the same time. Stronger acceleration, better gas mileage, etc. My blood pressure is lower too.
 
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