Dudule

Hi all,

I've been driving the all week end with the service light on for about 300 Miles...This is the first time I have this light on continously, it usually goes on and then off immediately. I took the code out and it's a 43 (knock sensor).
In addition to that I have a fan turning continously while the engine is on (I didn't open the hood to sort out which one) and my fuel burn is about 20% more than before...
I hope you guys can tell me WTF is the reason for this mess.
Thks in advance

skateparkdave

Sounds like you need a new knock sensor.Check its wiring all the way to ecm also. Other than that check all your fluid levels, brake, coolant, oil, trans fluid, even low power steering fluid can cause a check light.

Oh yeah, a 43 can be caused by bad gas or low octane gas. The knock sensor will retard timing to compensate. Probably the sensor though. You could clear the code and see what happens.

Dudule

Thanks skateparkdave,

Where is this knock sensor located ?
Is the fact that I have an increase in fuel burn means that I run rich ? Which would mean that m O2 sensor is in trouble?

skateparkdave

I just looked at your profile to see that you have a 92 lt1. I have a 90 l98. The knock sensor is located on the block mid way just above the oil pan on passenger side on l98. May be there but not positive on the lt1. Maybe someone will chime in.

tempest

the 92 has two knock sensors, one on each side just above the oil pan, midway at the block. they may be hidden behind triangular "shields. look for the single wire going to the sensor and you will find it.

sometimes if the knock sensor is not torqued in right it will throw a code too. if it accumulates crap it will screw it up as well. sometimes a good cleaning and a re-torqueing will solve the problem, but only sometimes.

the sensor are also coolant drain plugs, so get yourself some coolant and distilled water (and something to catch the coolant!) if you decide to yank the sensors out.

tempest

Dudule, are you sure code 43 is the only one that shows up? i doubt your fuel burn problem is caused by a knock sensor problem. O2 sensor is a good possiblity but since your fan is on constantly it could be other things.

Dudule

Thanks guys,

I'll have a look at that...

bogus

run by an Autozone or something like that and let them run some codes.... then you will get all the codes, and record them for better analysis.

CFI-EFI

I don't think bad gas will set a trouble code. If the engine is knocking and the ESC retards the timing, everything is operating properly, and shouldn't throw a code.

RACE ON!!!

tjwong

Ahh grasshopper, when DTC 43 sets the ECM or PCM will retard timing to a preset. Thus no advance which equates to bad MPG.

nmvette

I've got the same issue. The "service engine soon" light comes on after about two minutes of interstate driving. I bought the carchip E/X (diagnostic & log perfomance tool) today and will run it in the morning...hopefully it will give a code.

onedef92

The correct torque for your knock sensors is 15 lbs. Do NOT over or undertighten or you can cause your sensor to throw a false code.

Also, if you end up replacing one or both sensors, do NOT use anything other than the orange threading that comes on the sensor.

Sometimes the sensors just get caked with oil, grease, or grime and that will cause Code 43 to be stored on your ECM as well. I would clean and tighten both sensors to the correct specs first and see if that fixes the problem.

ittlfly

If either of the knock sensor connectors or their wires are loose, fallen off the sensor or other wise damaged, the car will run exactly as you describe.

runner140*

When I changed my radiator hose several months ago, it was a simple change but two things happened. 1. The service engine light went on.
2. The vette now gets 10% better gas mileage.

mikey whipreck

They will not throw false codes by overtorquing them...
They will give false knock by overtorquing them...

nmvette

So, I installed the SEMA approved Driveright Carchip E/X and found out very little. It passes the self test mode, (prior to turnig the engine over) but as soon as the engine is running it looses its connection to the vettes computer. Periodically it would re-connect but would promptly disconnect. I was unable to pull codes, develope an activity (trip) log or problem log. The MIL light comes on ONLY during interstate driving...about 2-3 minutes after reaching 65 MPH. Suggestions? Bad connections, bad sensors? Any info would help!

onedef92

That's what I meant. Thanks for the clarification. The point I was trying to make was they need to be torqued in at the proper specs to function properly.

MR.KIDD

When the check engine light came on (nmvette)your ecm should have stored the trouble code and should be able to retrieve the code unlest you have unhooked the battery or removed the ecm fuse or the car has seen 50 startups with no problems.As far as it losing connection it could be a bad connection or scan tool or ecm.On the light coming on after 65 mph in many cases I have seen the egr temp sensor was bad.
Hope this helps

reed62783

dudal -i have the same prob with my 92 . i have tried replacing the o2 sensors and it didnt help. i guess i need to do what they are saying.

nmvette

I am returning the carchip. Although it is supposed to be compatable, it has prongs for the sensor that are lacking the metal inserts. I cant imagine it being compatable or being able to retrive info with out that. So, I will need to pick up an actual scan tool. Any recommendation on brands? The Chevy dealerlship wants $600 for theirs (tech I or Tech II). I did discinnect that battery becuase I replaced the old one with an OPTIMA. But the MIL sensor has given me the light since then. I will check the temp sensor. Thanks!