I have searched, and have yet to find good info on code 43
89 RS LO3 i do have headers, and it is a single wire esc.
I have replaced the esc sensor and checked for voltage at the module and about i foot away from the sensor and nothing.
i have yet to find the ground for the sensor, any clues?
How does the sensor produce the 8-10 volts to send? does the connecter need to be connected for the sensor to produce voltage? just wondering if i could disconnect the connector and check the sensor for voltage.

 

You can eliminate the KS as a possibility by temporarily bypassing it with a 3.9K ohm resistor to ground in place of the sensor. Later ECMs require a 100K resistor, but your '89 should work with a 3.9K. If the code doesn't repeat with the KS bypassed, you can bet the KS or its wiring are a problem.

 

what do i connect the resistor to?

 

anyone? with the resistor idea i thought the sensor produced voltage.
I have searched ans still cant find good enough info.
I am also trying find the est wire. i have searched on this as well. My manual says it is at the firewall near the power brake booster. just about everything i have read on the board says it is on the pasenger side going over the heater box. i have been looking for this wire for awhile and nothing.
with code 43 and no voltage coming from the sensor i would assume that the timing would be retarded(haha). i checked with the est wire still connected and it is about 16-18* advanced.
anyone?

 

Code 43 on a TBI engine is common. Ninty-nine percent of the time it is because the forced knock test fails. Yes, the ECM attemps to force the engine to detonate, no detonation sets code 43. Here is a link that also contains other links that has more info then one may want. However, it will help in understanding and fixing the problem:

https://www.thirdgen.org/techbb2/sho...hreadid=231965

The '8746 ECM doesn't apply a voltage to the sensor. That style sensor and test apply to the SD TPI setups (and MPFI 3.1l V6). The LO3 knock sensor measures about 100K ohms.

RBob.

 

oops.

 

Here is some info.

 

part 2

 

Trickster that is exactly what i was looking for now i can start to troubleshoot the system. do you know where the ground wire connects to.
The code runs constant and i would like to take care of that before i set base timing. i did just find the est wire hiding under some other wires ecactly where i was not looking, over the wheel well
Rbob: i thought the sensor put out voltage to the module
Thanks guys.

 

The ground is a block ground. All of the ECM grounds go to the engine block.

Actually you are correct in that the knock sensor sends a voltage out to the module. This is a low voltage as the knock sensor is a microphone. A scope would need to be used with the trace looking like an audio signal (which it is).

The reason this can be confusing is that the TPI ECMs send a voltage to the knock sensor. The resistance of the knock sensor (3.9K) lowers this voltage. The ECM reads the voltage and expects it to be between two levels. If too low, then something is shorted, if too high, then something is open (something being the sensor or the wire to it). Sometimes I read the posts too quickly. . .

RBob.

 

well i have a tbi.
how does the ecm send a signal to and receive one with only one wire going to the sensor?

 

Actually, the knock sensor will send a signal to the ESC on pin "E" if it detects anything. The ESC will then send a signal from pin "C" to pin "B7" (Spark retard signal (ESC))of the ECM.

 

I was under the impression that the esc sensor sent an 8-10 volt signal to the module when no knock was present. As knock is detected the voltage is decreased. is this correct?
Thanks guys for the help!

 

That is correct.

 

The engine block ground. The outer housing of the knock sensor is the return wire.

RBob.

 

Not correct. The knock sensor is a microphone. The only signal it sends to the ESC module are the noises and vibrations picked up from the engine block.

The ESC module is an acoustic filter. It filters the signal (sounds) from the knock sensor looking for rapid frequency changes, excessive amplitude at certain frequencies, etc.

The ESC module will signal the ECM that knock may be occuring.

RBob.

 

What he is saying RBob is that the ESC sends a 12 volt signal to the ECM when there is a "NO KNOCK" condition. When the ESC receives a "KNOCK" signal from the KNOCK Sensor, the voltage from the ESC to the ECM drops and this signals the ECM to retard timing.

 

well guys i started going through the diagnostic steps Trickster posted. I discovered that it ckt 439 is open. I also noticed that the previous owner obviously was on the same track. the wire going to terminal b had a bit of insulation removed. I assume so he could test with the probe. I assume when you are supposed to probe terminal b that it is still disconnected from the module
I guess now i have to trace the wiring and find the problem?.

i cannot find a schematic for the tbi motor only tpi are they basically the same?

 

What part of it do you need?

 

i need to trace the pink/black wire(ckt 439) from the harness.
it says it is "open".
What exactly does that mean? Should i be looking for a broken wire or somethin?
I am sitting here at work, and trying to get all the info ready for tomorrow so i can tackle it without any setbacks(hopefully).

 

It means the wire is broken and no continuity through it. I will get you that other schematic.

 

Thanks for the help!

 

You have e-mail!!!!!!!!!

 

That wire has a splice in it from the factory. It is shown in the 1st pic above. Good possibility that the spice is broken (open).

Does anyone know where in the harness that splice is? Could save Lucky13 some time in locating it.

RBob.

 

already been sent to him and it has two splices. One near the fuse block and one near the ECM.

 

Trickster thanks for all the help. I have successfully tracked the wire behind the block past the heater box and behind the fender.
from there it comes into the cab through the wire harness behind the door jam(passenger side) i removed the kick panel and saw the small pink/black wire. it was disconnected!
I removed the lower cover to the dash assembly on the passenger side and saw a larger pink/black wire crimped together w/ the smaller pink/black wire.
The other end of the crimp was empty.
The larger wire is the ign source, while th small wire continues to the ecm. I spliced the wires back together and no more code(for now).

I put this info down so the thread doesnt get left hanging with no finalization, as i have found alot of them. hopefully it will help someone else

Thank you for your help!:rockon:

 

Glad to help out Lucky 13.