Fault code 12 Help!!

[Holmsey]

Hi all, been using my Truck with 1993 Lexus LS400 power for around 10months. Always started up first crack once or twice it has cut out, no tick over and then was reluctant to start, but always did after turning over for a few seconds Mostly while I've been using it it has started no problem and drove perfect.

Used it the other day started and ran perfect, drove 7 miles parked up for 45mins and came to start it and it just turns over and no fire.

Tried and tried but still no fire, came up with fault code 12 (RPM signal 1) I swapped out the crank sensor from a spare old engine just the same.
Any pointers to where I go from here? could be I have two faulty sensors though I did fit a new one when I fitted the engine into my truck originally.
Help!!! ;o)
Holmsey (UK)

 

[Holmsey]

Or can someone give me the genuine part number. As numpties here can only give me the correct part if I have the part number or reg Derrrr.

 

[gloverman]

Crank sensor for all gen 1 and gen 2 engines is 90919-05002. It should be on the top of the sensor if genuine.

I work on heaps of these engines and have only had a couple of stuffed crank sensors other than physically broken ones.

Most common cause for code 12 (or code 13) is incorrect cam timing.

Has the ecu had new caps? Also damaged front loom or poor connection on the connectors by #1 injector.

 

[Holmsey]

Hi Gloverman thanks for advice, ECU has had the caps replaced. I did fit a new cambelt when I put the engine together done 3500 mile ran like a dream, could it be wrong? I will double check.
My sensor is Denso but no numbers on it, one off spare engine is also Denso but does has those numbers on it. Resistance on both is the same when tested with meter.
I will try and strip back the wires on front loom and check connectors by #1 injector...

 

[Holmsey]

One thing I do find weird and may pinpoint the fault to an expert liked you Gloverman.. Is if I turn off power to ecu that normally removes the faults. Now it doesn't do that.. As soon as I supply power back to ecu the fault code 12 is there without even trying start the motor.

 

[George_R]

You must have wired STA pin the very wrong way.
Disconnect it, check again

 

[Holmsey]

Just double checked cam timing that was OK. Pulled and checked the wires and connectors by injector #1 couldn't see any faults. Reset fault codes ... Got constant flashing no fault light...??? All I did do was clean out the crank position senor connector, bit of fuzz on the dizzy cap contacts that was it ...and it's started right up??? Think I must have an underlying fault that probably will come back to haunt me... Just finding out what.. I suspect it's the crank position plug in connectors ..but we will see ..thanks for help.. Out of interest what is the STA pin?

 

[Holmsey]

So engine is running again... Not sure what caused it to not fire up. can a fault code if not removed stop an engine from firing up?

 

[Bushwhacker]

Hi Dave,
You probably have a break or intermittant connection in the wires, in or near the grey multiplugs you were tugging at next to #1 injector. The wires in them go down to one of the coils, the cams and the crank sensor. Code 12 might be to do with one of the cam sensor wires and probably what prevented the engine from starting or cutting out especially when the loom gets hot after a run and expands slightly?

 

[Holmsey]

Cheers Vince (good to hear from you) and Gloverman for advice ...I'll have a better look and see if I can replace the plug in connectors with something.