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Posted By: DrCaldre 1987 G20 Code 43 - August 08th 2020 10:38 pm
I've made this post after searching and reading many others here, and elsewhere.

I've got a 350 TBI. All stock. Code 43 from the check engine light as per the mechanic has told me.
The van runs and idles fine.

I don't have the van back from him yet, but I should this coming week. He has sort of tasked me with diagnosing this so we just don't end up throwing parts at it.

I plan to bridge the connectors and read it again. It'll be good to know how to do that.

I've searched around the internet quite a good bit, and I find different suggestions and solutions in each place I look.

The CEL comes on when the van is started. The "BRAKE" light is also on, mechanic found the valve to it is closed, meaning there was a leak at some point. A friend and I plan to replace the whole drum system.

I need to figure out what is causing the CEL without spending money on parts I don't need. I'm decently smart, and I have a multimeter. Everything I've read about this is for engines that are running poorly. The steps and suggestions are written horribly, the posts written long ago, scattered around different off-roading and chevy websites.

I'd really like to tackle this problem when I get the van back. I've got long tube hedmans and the full exhaust system ready to go on, and I plan to have an 02 bung put in. I obviously want to solve this CEL before having the exhaust done, as well as so the CEL is actually a working warning light, and not always on.

I'm doubtful that there is any single source of truth for troubleshooting the code 43, but I would really like to formulate a concrete attack plan. I appreciate the help ya'll.
Posted By: frscke1 Re: 1987 G20 Code 43 - August 08th 2020 11:12 pm
typed it in google and ...

Knock Sensor Error
The ECM receives a signal from the Knock sensor based on the amount of engine ping detected. The ECM uses information from this sensor to help calculate fuel delivery and spark timing.
Posted By: DrCaldre Re: 1987 G20 Code 43 - August 09th 2020 12:27 am
Thanks frscke, I obviously found that too. The coolant is behind that sensor. I have seen a lot of folks online saying how changing the sensor didn't banish the CEL. I'm a bit hesitant to spend the money on the part, and drain my coolant, without doing a little more troubleshooting.

Here's one of the posts I was talking about, it's not really something I can read and follow. I was hoping someone here might have a little more domain knowledge.

https://ck5.com/forums/threads/code-43.215245/
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