Error codes 37 and 43. Truck is new to me.

[thinger2]

So I recently bought this truck and while running through it and checking for any problems it may have the headlight switch burnt up and since I had the bezel out I took the instrument cluster out to check all of the bulbs. I realized that someone at some point had removed the service engine soon light and replaced it. I have codes 37 and 43. 43 is easy enough I will go get a knock sensor and replace it but what do I need to do to fix code 37? It says that 37 is Torque Converter Clutch Brake Switch Circuit Error. That is fine and I know what it is but how do it go about fixing it. I cant seem to find any info on this code.

1993 Sierra C1500

Did you figure out why the headlight switch had burned up?
43 is knock sensor and its wiring but I see youve already done that.
37 is almost certainly the brake light switch.
It is such a commen failure that It is not worth the time to diagnose it.
Get a new switch. They are a real pain to replace.
The clip that holds the switch onto the brake rod tends to either fly away or go into your eyeball.
You can get a spare clip from Dorman.
I recomend that you spend the three bucks so you dont have to chase that thing.
And wear safety glasses.
This might not solve all of your problems.
But I can gaurantee you that those parts are bad or intermittantly failing.
You can chase your tail forever if you get screwy results depending on if the engine is hot or cold or if you hit a pothole or whatever variable.
Everybody calls it the "Parts Cannon"
Replaceing all of the sensors and rebuilding the TBI and repairing all of the grounds is not firing the parts cannon.
Replacing random parts expecting that it will solve a problem is firing the parts cannon.
They are one of the most reliable platforms ever built.
But they are old.
Pop the hood, take the TBI off and rebuild it, Peel all the wiring all the way back to the firewall and fix it.
Repair all of the grounds.
Chase the wiring all the way back to the bed and fix it.
Set aside one weekend a month that is nothing but truck work.
Do that every month and within a year you will have all of those systems repaired.
You can essentially build yourself a new truck if you dont get discouraged and loose your marbles.
I have about 280k on mine.
factory engine and factory trans.
I gas it up and hual ass from Seattle to Detroit and the only downside is it doesnt have heated mirrors.
I bought this truck something like 12 or 13 years ago for 2 thousand bucks
Im probably into it for about 4 grand in parts over 12 years including brakes and plugs and a radiator etc..
Many, many hours of reparing and upgrading every part of the wiring.
The old saying.
How do eat an elephant?
One bite at a time.
Now I have a truck that I wouldnt hesitate for a second to drive deep into Mexico.
And it is about 60 thousand dollars cheaper than a new truck.
That spare 60 spread across about 40 years of fixing my own crap and not having a car payment is why I own my house free and clear and thats how the kids went to college.
It us really easy to get discouraged and frustrated and think that it is all beyond you.
Especially when gatekeepers decide that you havent met whatever absurd thresehold.
That is just not true.
Everybody started out not knowing **** all about anything.
Car culture can be great. You can meet some amazing people who become life long freinds.
Same with racing. You can meet incredible fine people.
But some of those people can be the worst gatekeeping little princess tiarra crown wearing butt hurt posers.
Car show vultures.
The ******* guy who has a a couple of standboards with all of the pictures of the stupid amount of money he spent on yet another 1st gen Camaro and his wife has a box of piss warm ham sandwiches but that **** aint gonna eat becuase he just caught you out for having aftermarket door lock knobs.
He doesnt give a **** that his kids moved the **** out when they were 15.
He doesnt give a **** that his wife is gonna cut off his IV when nobody is watching.
He has OEM parts and your window crank isnt up to *****.
We call them "Car Queens"
The bondo brigade.
They paid somebody to build the car.
They trailered it to the show.
It is an undriveable plastic **** wagon.
This guy has spent more time and more effort on accumilating his tee shirt collection from various car companies that have nothing to do with his car.
Hes about 5 foot 9 and shaves his head and has some 1990s tribal tatoos and a barbed wire tat but he doesnt know what it means.
At least twice divorced and hangs out at strip clubs cuz he is sure that Candy really digs him and he can save her.
True love.
It is hard to sort those with good intentions from those who enjoy tearing you down.
You can do this. You can figure it out.
You just have to keep at it.
Dont give up.
I am the company clown on this forum.
If I can make this old **** run you sure as hell can do it too.

 

[marshallsmith27]

Yes I did find out it was the headlight switch. I took it out and it was definitely the smell from the smoke I had been smelling. Very easy fix and headlights were working right away.

As for the 37 I’m not sure because it’s not throwing a code anymore. Still no cruise. I’m going to just replace it tomorrow. I felt the diaphragm on the egr valve and it’s stuck. not sure if it’s opened or closed but I’m going to replace it tomorrow also.

This 43 is all I have left. Brand new knock sensor and brand new connector. but like I said this truck doesn’t have the electronic spark control module so that doesn’t leave anything else, right? If I remember right last night on the first ride back from the mechanic when I was at highway speed and let off the gas the light would turn off and soon as I gave it some decent pedal it would come back on. The mechanic also swears this truck is supposed to have an o2 sensor on the header and downstream but I don’t see that anywhere. Is he wrong?

 

[marshallsmith27]

I should also mention code 43 comes on as as engine is turned on

 

[DerekTheGreat]

An electrical motor turns on, an engine starts.

Yes, if you've still got factory exhaust manifolds the O2 sensor will be located just upstream from the exhaust manifold collector. It's on the driver's side and will have just one wire going to it. By 1993 the ESC module may have been relocated inside the ECM, I was surprised to see it on the '92 I had. Although if your truck has the external one, it's located near the passenger side rocker cover near the throttle body, can't miss it. However, I doubt that's what your problem is. Both my '89 and that '92 someone had ripped the wire going to the knock sensor. So your "Hot rod mechanic" may have actually jammed a new knock sensor in along with a connector, but the wire may still actually be broken somewhere else along the line. Investigate that first.

 

[marshallsmith27]

@DerekTheGreat So I just checked everything and the wire seems to be fine. It disappears at some point but like it was said it more than likely runs to the computer inside the truck. I just did a once over again for the knock sensor even though when I picked up the truck he showed me what he did. He ran some corrugated tubing over everything he redid. he did a great job on that and I went ahead and replaced the egr valve and the solenoid because the valve was a little sticky and I could tell it was original. The only thing I’m not sure is whether or not it was torqued or not to the right 15ft/lbs and I also should have checked the resistance of the knock sensor itself before dropping it off. I think these are supposed to be 99.9k and not the 3.5k?

You must be registered for see images attach

 

[Schurkey]

Connect a scan tool, drive the vehicle long enough to warm it up. Step on the gas hard. I'd expect to see a few knock counts on the scan tool, showing that the knock-sensor circuit is complete and the sensor is functional. At the same time, look for spark retard showing that the ESC is functional.

Fifteen minutes with a scan tool saves hours of guessing and tracing circuits manually.

True enough, this does not verify that the sensor is correct, or properly torqued; or that a stand-alone ESC is the correct part number/calibration for the vehicle. But testing with the scan tool is a fine start.

 

[marshallsmith27]

@Schurkey Where do I get, buy or rent a scan tool? This is new to me. I will gladly buy one. I thought ODB1 couldn’t do any of that?

I will get a scan tool tonight if that’s what it takes. Link?

 

[someotherguy]

Your 1993 C1500 is first year for the spark control module to be built into the PCM, this is generally true on the light duty automatic transmission trucks. The mounting plate on the passenger side of your TBI unit will just have a big blank square area where the module would have been if your truck was a little older. The PCM's don't often go bad so the problem is likely elsewhere - incorrect sensor, bad wiring, etc. You're on the path with the advice already given, just thought I'd jump in with this so you're no longer confused about not seeing an ESC module on the truck.

Richard

 

[Schurkey]

@Schurkey Where do I get, buy or rent a scan tool? This is new to me. I will gladly buy one. I thought ODB1 couldn’t do any of that?

I will get a scan tool tonight if that’s what it takes. Link?

I don't know of anyone renting a scan tool. There's a member here who's donated one for "community" use. I'm not watching that thread, I don't know how long the waiting list is by now.

GMT400 - Community Scan Tool

Truck running rough? Maybe you want to throw some parts at the 'ole girl to make it right. But which part? There are so many. Perhaps you were in the driveway with the hood open, intensely staring at the engine to telepathically coerce it into functioning again when your neighbor stops by. His...

www.gmt400.com

Be aware that a "code reader" is NOT a scan tool. A scan tool will read codes--and so much more. "Code readers" are consumer-grade garbage, as is the "paper clip solution".

When it was me, I bought used PROFESSIONAL GRADE scan tools from sellers on eBay. Most recently, a Snap-On Solus Pro with 8.2 (2008, second quarter) software, various vehicle adapters and cables, a battery that has some life left in it, and a suitcase to carry it around in. $350 shipped to my door. Before that, I spent over a decade with a Snap-On MTG2500 with 6.2 software, but it was damaged so I replaced it. Snap-On has ended support for the '2500 series, the Solus, the Solus Pro. They may have ended support for the Solus Ultra. NO repairs, NO updates to software. NO accessories except what also fits the newer tools. The Solus Edge is newer and still supported, and the Solus Legend is the current model last time I looked. Newer tools are more expensive. There are competing brands of professional-grade scan tools but I have no experience with any but the Snap-On line.

Other folks seem to like software + cable, or software + dongle, and a laptop. Never used that. Can't give an opinion except to say that lotsa folks with software solutions have to buy extra "pids" to do anything useful.

Consumer-grade scan tools as commonly sold on Amazon and in your local parts store, tend to have minimal usefulness--they may receive info from the computer, but may not communicate with the ABS, air bags, body module, instrument cluster, etc. And/or they may have no bi-directional control--the ability to tell the computer to perform certain functions like vary the idle speed, or turn on all the warning lights on the instrument cluster to see if some are burnt-out.

What can a scan tool do on an OBD-1 vehicle? This is my previous scan tool, connected to my '88 K1500. The entire thread has back-story, but posts 14--15 have the scan tool info.
www.automotiveforums.com/vbulletin/showthread.php?t=1146067

94 k2500 no low end power and horrible fuel mileage - Automotive Forums .com Car Chat

94 k2500 no low end power and horrible fuel mileage C/K

www.automotiveforums.com

 

[DerekTheGreat]

Schurkey's advice is great. Although I want to say the system attempts to test itself. What I remember reading about that is if it doesn't see knock after awhile it will advance timing until it is "certain" that it should. If it still doesn't see knock, it sets the code. My truck would do this. Would be driving casually down the road at 25mph and suddenly there were skittles rattling around in a can followed by the Service Engine Soon light. Although if I remember correctly you said the code sets right away. That seems to suggest a break in the wire somewhere.

My '88 Service Manual has this to say about code 43:
"
Code 43 indicates that the ECM is receiving less than 6 volts for a 4 second period with the engine running. If code is present, refer to Code 43 chart in Section 3..
"
Here's some diag that might help:

You must be registered for see images attach