Code 12:Engine revolution signal missing...WTF?

[Amamet]

just picked up my 1988 fj62 from having the exhaust replaced and noticed the check engine light on. the tech at the shop said it was a code 12, Engine revolution signal missing or something like that. the check engine light had never come on before and certainly wasn't on when i dropped the truck off. any ideas where i should start?
thanks
allen

 

[TobyB]

Under the distributor cap. Look at the gaps, and the connector to the distributor.

t

 

[Amamet]

I don't really believe in coincidences, but any reason a new exhaust would trigger this code? I have a local autozone nearby and figured I'd have then scan the truck again just in case. Where is the port located?
Thx
Allen

 

[slcfj62]

Autozone won't help. This is an early OBD with a unique method of determining the code. See here for how to:

https://forum.ih8mud.com/threads/reading-3fe-engine-codes-at-home.115780/

 

[Amamet]

thx for the info...just ran the codes myself, looks like 2 flashes and 8 flashed then 5 flashes and 1 flash. guess thats a code 28 and 51. 28 would coincide with new exhaust work but what about 51, switch signal? cant figure that one out yet

 

[Amamet]

well since i didn't have a check engine light before the exhaust work and the first error code is for the o2 sensors, can the second error code ,51, be a result of the first?
thx
allen

 

[slcfj62]

A code 51 is your throttle position sensor and shouldn't have been effected by the exhaust work. Odds are the code 51 has been there a while. Does your engine idle faster than 650 rpms? Here is a thread I started some time ago for my experience with the code 51.

https://forum.ih8mud.com/threads/fj62-3fe-idle-problems-finally-fixed.273855/