Chasing SES Code 43

[echoxozzy]

Like the title says I am chasing my tail trying to figure out what is causing this.

Background on the truck. It is 1989 V1500 Suburban. I recently replaced engine with a Blueprint crate engine. While this was being done I had the transmission rebuilt. Exhaust was previously leaking from every joint so had that rebuilt. Couldn't get the manifolds off the old engine so replaced with shorty headers. The only other change was an Edelbrock intake.

Once it was back up and running I was getting codes 32 and 43. No noticeable issues as far as performance other than the SES light. I replaced the EGR valve and 32 went away. 43 persists but only appears if I really stomp on the gas. I can drive around all day in town (55 and below) and nothing pops. Based on what I have read on the internets I think that I am getting the code when the forced knock test fails twice.

I knew I was getting code 32 before the engine change. It had been there since I got the truck a few years ago. I never got code 43 before the engine change but I also wasn't checking codes very often since I expected 32 to pop up just about any time I drove above 45mph.

Since then I have:

-Replaced the Knock Sensor with ACD P/N 231-324. The one that had been installed looked very similar but had a black nub
-Checked static timing. It was 2 deg advanced. Moved back to 0.
-Validated connection between knock sensor and ESC module (P/N 16052401). P/N noted because some threads indicated that folks are getting the wrong (but similar looking) knock sensor form parts stores and that they needed to be paired with the correct ECS module
-Tried to trip code 43 by banging on the engine block near the sensor with a wrench. Tried this with both the engine on and with key on (engine off). Went at it pretty good and never could get the SES light to come on. This reinforces to me that the SES light is for a failed forced knock test.

Questions that I know I have for the crowd:
1. Am I on the right track thinking it is failing the forced knock test?
2. How many Ohms should my knock sensor read? I checked the black nubbed one and it read 99kOhms. I've read that one knock sensor should read about that much and another that reads around 4kOhms. Can't find anything that says which is correct for me, just that I should make sure I have the correct one. For what its worth I saw a youtube video of a guy checking the white nubbed knock sensor and it also read the 100k(ish) kOhms.
3. Is that the correct knock sensor for the ESC module I have? How could I find out?
4. Should I have been able to trigger the SES light by banging on the engine block next to the sensor? If yes I think this leads towards a problem with the sensor or ECS module?
5. If no to item 4 I am leaning towards the temp sensor. Could the single wire O2 sensor also be the gremlin. I am wondering if my exhaust changes are hiding something there.

I don't really like throwing parts at the problem but haven't seen anything that would lead me to be able to troubleshoot this to the culprit. Thanks

 

[Schurkey]

Background on the truck. It is 1989 V1500 Suburban. I recently replaced engine with a Blueprint crate engine.

Interesting. Photo associated with that web page shows them using their own aftermarket block, which does not have proper provision for a water pump bypass passage. It's machined like a Vortec block, with no coolant bypass drillings. Is that the way your engine came?

43 persists but only appears if I really stomp on the gas. I can drive around all day in town (55 and below) and nothing pops. Based on what I have read on the internets I think that I am getting the code when the forced knock test fails twice.

-Replaced the Knock Sensor with ACD P/N 231-324. The one that had been installed looked very similar but had a black nub

Advance Auto claims that's correct for an '89 V1500 5.7L. Maybe their catalog is wrong. You could double-check on other web sites including ACDelco's.

Was it torqued into the block appropriately?

-Validated connection between knock sensor and ESC module (P/N 16052401).

HOW?

-Tried to trip code 43 by banging on the engine block near the sensor with a wrench. Tried this with both the engine on and with key on (engine off). Went at it pretty good and never could get the SES light to come on. This reinforces to me that the SES light is for a failed forced knock test.

If you do this with the engine running, I'd expect the idle to slow as the timing is retarded. You should see the timing retard when using a timing light also. That confirms that the knock sensor is sending a knock signal, and the ESC/Computer can retard the timing as a result. It does not confirm that the knock sensor sensitivity is correct--just that the system "works".

I have no idea why that would set a code. The computer doesn't know you're testing the knock sensor. If the sensor doesn't report knock...the computer thinks everything is fine so it doesn't retard timing, and doesn't set a code. If the sensor does report knock, it retards the timing briefly, but doesn't set a code because retarding the timing "stopped" the knock.

Questions that I know I have for the crowd:
1. Am I on the right track thinking it is failing the forced knock test?

Download the service manual set for your vehicle from the links in the Sticky section of the Engine web page. Follow the diagnostic procedure.

If there's no manual for a V1500, you'll have to make-do with the C/K manual and hope the squarebody system is the same. Your truck had a "VIN K" engine...right? Or find a V1500 manual from another source.

I bought most of my manuals as "used" paper copies from sellers on eBay. I have a couple of manuals on DVD-ROM, and a few downloaded from this site.

2. How many Ohms should my knock sensor read? I checked the black nubbed one and it read 99kOhms. I've read that one knock sensor should read about that much and another that reads around 4kOhms. Can't find anything that says which is correct for me, just that I should make sure I have the correct one. For what its worth I saw a youtube video of a guy checking the white nubbed knock sensor and it also read the 100k(ish) kOhms.

Verify with the service manual.

3. Is that the correct knock sensor for the ESC module I have? How could I find out?

No real idea. You'd have to cross-check the application with ACDelco, I guess.

4. Should I have been able to trigger the SES light by banging on the engine block next to the sensor? If yes I think this leads towards a problem with the sensor or ECS module?

I don't see how that would trigger the SES light.

5. If no to item 4 I am leaning towards the temp sensor. Could the single wire O2 sensor also be the gremlin. I am wondering if my exhaust changes are hiding something there.

I don't see how a coolant temp sensor, or an O2 sensor, can trigger a code for the knock sensor.

Clear the codes, connect a scan tool, look for knock counts as you drive around trying to set the Code 42., verify ALL the other sensors and computer outputs.

 

[echoxozzy]

Interesting. Photo associated with that web page shows them using their own aftermarket block, which does not have proper provision for a water pump bypass passage. It's machined like a Vortec block, with no coolant bypass drillings. Is that the way your engine came?

I don't have the background to be able to answer this.

Advance Auto claims that's correct for an '89 V1500 5.7L. Maybe their catalog is wrong. You could double-check on other web sites including ACDelco's.

Was it torqued into the block appropriately?

Validated that the part number was correct on ACDelco's site.

Torqued to 14 ft-lb.

HOW?

Checked continuity in the wire between the connection to the knock sensor and the ESC module.

If you do this with the engine running, I'd expect the idle to slow as the timing is retarded. You should see the timing retard when using a timing light also. That confirms that the knock sensor is sending a knock signal, and the ESC/Computer can retard the timing as a result. It does not confirm that the knock sensor sensitivity is correct--just that the system "works".

I have no idea why that would set a code. The computer doesn't know you're testing the knock sensor. If the sensor doesn't report knock...the computer thinks everything is fine so it doesn't retard timing, and doesn't set a code. If the sensor does report knock, it retards the timing briefly, but doesn't set a code because retarding the timing "stopped" the knock.

I'm following you. I'll check this again using the timing light. I doubt I was doing this long enough to make it think there was a knock it couldn't compensate for.

I'll dig through the manuals later and see if they match up. My truck did have a VIN K engine.

Thanks.

 

[echoxozzy]

One symptom to add. Engine documentation said to set timing using the total timing method. When I checked that, I was getting 20 deg adv at idle and 40 at 3500 RPM. Should have been 10-16 at idle and 34-36 at 3500 RPM. This is with static set at 0. No other updates.

 

[Schurkey]

I was getting 20 deg adv at idle and 40 at 3500 RPM. Should have been 10-16 at idle and 34-36 at 3500 RPM. This is with static set at 0. No other updates.

I didn't think TBI programming allowed anywhere near that much spark advance.

I'd have expected something like 12-ish degrees at idle, and 30 at 3500.

 

[echoxozzy]

I didn't think TBI programming allowed anywhere near that much spark advance.

I'd have expected something like 12-ish degrees at idle, and 30 at 3500.

It is running premium fuel right now. Would that result in the computer allowing more spark advance?

 

[Schurkey]

NO reason to put "premium" fuel in a TBI truck engine.

Far as I know, the computer timing advance is limited by the programming, not by the fuel used.

 

[echoxozzy]

Download the service manual set for your vehicle from the links in the Sticky section of the Engine web page. Follow the diagnostic procedure.

If there's no manual for a V1500, you'll have to make-do with the C/K manual and hope the squarebody system is the same. Your truck had a "VIN K" engine...right? Or find a V1500 manual from another source.

I bought most of my manuals as "used" paper copies from sellers on eBay. I have a couple of manuals on DVD-ROM, and a few downloaded from this site.

Using this flowchart from the pubs. Now I don't have a scan tool but I am pretty sure there is no knock at idle. I went on to test 2 and verified with a timing light that timing does get retarded a couple of degrees after I tap on the engine block with a wrench. So Cod 43 is intermittent and it leads e to a part of the manual where it seems like you hunt to other symptoms to find the culprit.

I think what I noted above about total timing being high is a pretty good place to start. I haven't been able to find anything using the google machine that discusses things that could cause too much advance.

Any ideas?

Also. Since scan tools seem to be at a premium I was looking at getting one. I see there are a couple of bluetooth ALDL adapters out there. Are those any good? I'm not looking to tune this thing for higher performance. Just being able to troubleshoot problems like this,

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[echoxozzy]

Hooked the scanner up today and there are a few knocks detected when I turn the truck on or off. No accumulation at idle or when I drove around the neighborhood.

I still have the problem with it advancing timing too far. (20 initial and 40 total)

I did notice with the scanner plugged in that it idles faster than I expected (1k RPM). That drops down slightly when I put it in drive. When I put it back into park after driving around it started idling at 2k RPM. This higher idle went away if I turned off and restarted the vehicle. All this is with the truck warmed up. Temp was staying between 200 and 210 F.

I know this probably wasn't the most scientific approach. Was mostly getting familiar story TunerRT.

I did notice that TunerRT never displayed a value for SparkAdvance or HiWay AFR.

 

[hclanton93]

I had an issue with my truck throwing a code 43 right at startup. Apparently there are 2 different knock sensors for these trucks. The one you posted is the white one, which is what I had. I replaced it with the black one and it fixed my issue. This is just a thought