Car will not start after reaching normal operating temperatures, code 43

THOMAS LAWRENCE

MEMBER
1989 BUICK CENTURY
3.3L
V6
2WD
AUTOMATIC
111,000 MILES

This car has sat for about 5 months as it used to be my daily driver. I replaced the coil packs, plugs, plug wires, knock sensor, starter, and crank sensor. It is still giving a diagnostic code 43 and will not start when warm and sometimes wont start cold. There is no pattern that I have found of it not starting, but I was wondering if it would be injectors or ICM? I have 3 parts cars with the parts that I have mentioned but was wondering which I should try first. The hood was left up for about a month because I forgot about it.

1 Reply

JACOBANDNICKOLAS

MECHANIC
108,269 POSTS

Hi,

It could be related to the ICM, but I have a question. When it fails to start, do you lose spark to the plugs? I ask because the code you have is related to the knock sensor. I can't imagine it is going to change timing enough to prevent starting, but anything is possible. Also, the ICM can be the issue. I believe this one is mounted under the coils. Is that correct? We used to call them digital ignition control modules. I just want to make sure we are on the same page. And yes, they commonly went bad, but when they did, spark was lost.

Let me know if you have spark when it fails to start. Here is a link that explains what to do. Do this or simply see if it starts for a couple seconds using starting fluid.

https://www.2carpros.com/articles/how-to-test-an-ignition-system

As far as the knock sensor, voltage to it should be between 4v and 6v with the key on engine off. If you are getting between that amount of voltage from the ECM, replace the sensor. If it's over 6v we have a short to power and less than 4v indicates a short to ground. Either variations can indicate a poor connection at the ECM or a faulty ECM.

Let me know what you find.

Take care,
Joe