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infamous code 43



Not to beat a dead horse but have read about this problem many times and still confused so plz bear with me.

What I have:

1993 gmc 1500 sierra p/u, 4.3tbi, automatic


Plz note problem I have has been going on for about 7 years now and I just installed new longblock and problem still exists


* code 43

* 2 dead cylinders

* low operating temp

What I've done:

* installed new motor

* installed new knock sensor

* installed new ignition module in distributor



Not sure where esc module is. In ecm? In distributor?

Why do I have low operating temp?





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10 answers to this question

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Connect a timing light to each spark plug wire,if there is current the light will flash.If any cylinder doesn't light up back track to see where the problem is.


How old are the spark plugs & wires?Did you install new ones with the new engine?Did you check the gap?


Are the heads in good condition?

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Oh boy. So this engine you installed isn't running right either? Fix that first. No it won't fix your code 43 but it'll get you going. Code 43 is set because of an electrical issue in the system, NOT because of a misfire. If your wiring is good, then you need a PCM more then likely, according to all-data, your truck doesn't have an ECM becuase it's an automatic transmission.


Knock Sensor System

All gas engines are equipped with a knock sensor system. A knock sensor is mounted on the engine block. On vehicles with a manual transmission, the sensor is connected by a blue wire to the knock sensor module, which is bracket mounted on the top of the engine. The sensor, in response to engine knock, sends a signal to the module and from there to the ECM, located in the passenger compartment. The ECM sends a signal to the distributor to retard timing.

If the vehicle is equipped with an automatic transmission (4L80E or 4L60E), a PCM (powertrain control module) is used instead of an ECM. The PCM performs all ECM functions and also provides electronic control for the transmission. It is located in the same place as the ECM.

NO knock sensor module is used on a vehicle equipped with a PCM. Instead, the blue wire from the knock sensor is wired directly to the PCM.

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Hey fellows I finally got the miss out of my new 4.3. At first I put in a spare distributor. Ran great for 2 days then started missing again. Finally checked spark plugs. Gap was only .025 and four plugs were loose. That problem is solved.

However engine temp is still only 160degs and I did verify that with a temp probe stuck in radiator. I would like to solve this problem before getting back to the original code 43. Any ideas? Just so you know I did put in a brand new 205deg thermostat upon new engine installation and my old motor also ran at 160. Help!

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Could the ESC/ECM hear the "noise" from my 2 dead cylinders and mistakenly throw the infamous code 43?


Remember I said I installed new longblock. New and old motors both had/have 2 dead cylinders. Runs like crap. Was thinking its distributor cuz its the only thing common between the new and old motor. Hoping that by installing another distributor it takes care of 2 dead cylinders and therefore eliminates excessive engine noise and maybe stop throwing code 43

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Thanks guys

As far as low temp goes that too has been going on for years even with new thermostat and sensors. It might be intake gasket related as last 2 motors I put in truck both ran low temp. Gasket kits came either with 2 sets of intake gaskets or 1 set with removeable piece for water that flows through intake. Unless low water temp has anything with crappy way motor is now running I will address that later.

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Mr tlj - thanks for link. Although I am capable of diagnostic work id rather just replace parts. Can you tell me where esc module is on my particular truck? This seams to be a controversial subject . I can tell you its not mounted on motor. I am going to swap distributors this week as its the only thing left on my new motor that was on the old motor



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