I have a 1989 Formula 350 TPI. Check engine light shows code 43. Bought 3 different knock sensors. Still have code 43. After looking at several forum posts, I see there are 2 different sensors, a 3.9K ohm and a 100K ohm sensor. All 3 I purchased were 100K ohm. For test purposes, I installed a 3.9K resister in place of the knock sensor and code went away and SES light turned off. I cannot figure out how to order the correct knock sensor The last two I ordered were one for a 350 and the other one was for a 305, both were 100K.. Does anyone have the part number for a 3.9K knock sensor? Thanks This car is kicking my butt.

 

FWIW, this is what I installed when I converted from 305 to 350: ACDELCO 21392
This 3.9k sensor works perfectly in my 90 speed density TPI, though your 89 probably has an external knock filter which would call for a 100k sensor.

 

The 100K sensor definitely does not work. The code go away with the 3.9K resister in place. I'm sure the 3.9 sensor will work. This car is so jacked up, there's no telling what's been done to this car. It has been an electrical nightmare !! Thanks

 

ya, looks like different years had different part number, someone needs to break out the parts book for you to confirm, but its all over the internet.

https://www.gmpartsgiant.com/oem-pon...ck_sensor.html

 

RT66er, Assuming my '89 had an external knock sensor, where would it be and what would it look like ? Thanks

 

Passenger side of engine - in middle, under cooling jacket plugs

 

I take it the knock filter is the same thing as the Knock sensor ? Would that wire go to the distributor or the ECM ?

 

Knock sensor wire goes to esc module on the bracket next to master cylinder.

 

the only devices near the master cylinder is the fuel pump relay and I think MAP sensor (small module with vacuum hose going to intake and one 3 wire plug) Would that be it ?

 

What ecm do you have someone convert to a 1227730 ? No map on 89

 

Mine definitely has a MAP. ECM sevice number 16196344 and it says it's a remanufactured module

 

Are you sure your cars not a 90 ? The knock filter is part of the memcal. The ls
ks wires directly from ks to ecm. Could be a faulty ecm or connection at ecm have you followed the troubleshooting guide ?

 

production date of the car is May 1989. Maybe it's wiring as a 90?? Do you have a link of the troubleshooting guide handy ?

 

One more thing, I looked up the 1227730 ECM, it only has 2 connectors on it. Mine has 3, 2 black and 1yellow

 

 

730 has 3 connectors yours has been replaced with a superseded number

 

I have a few if you need one

 

So can I still use the Troubleshooting guide you posted ?

 

Yes your using 90-92 parts 3.9k ks

 

Thank you very much !!

 

Post your findings, welcome

 

1 more question, how do I find the pinout for all the connectors on the ECM? Example CKT 496

 

Pin F9 at ecm
its labeled there
https://tpiparts.net/1227730_pinout_diagram

 

Looks like Brian's (tunedperformance) got you covered... he's a very good reference source.

 

Get it fixed ?

 

Ok, Problem went away. I replaced the knock sensor with the 3.9K sensor and check engine light still came on. unplugged ECM and checked continuity from sensor to Pin F9 on ECM. Perfect there. Put everything back together and haven't had a problem since. Looks like maybe just reseating the connectors solved the problem ?? Thanks for all the help!!

 

Good to hear 👍🏻