cypher85

Greetings,

My 1990 is throwing Code 43 whenever it starts. I have modified it with a 383, superram, afr heads and supporting mods. The chip is a pcmforless mail order tune. I have replaced the knock sensor, new plug wires and plugs, new cap, new coil, new rotor. Voltage at knock sensor is 4.97 and the ground is good. I replaced the computer around 4 years ago with an aftermarket.

While driving with a scanner hooked up I see absolutely no retard of timing when the engine light comes on. Car never loses power. One thing I have noticed is that every time the car is started it seems to have to relearn like if I disconnected the battery. It also stinks pretty bad.. but I think that has a lot to do with the tune and lack of cats. Idles fine around 1000.

I have read up on threads that have similar issues, I can't decide if I should replace the Ignition module or memcal or both. Or maybe it is something else entirely.

The motor was just rebuilt. Any help is appreciated.

Cliff Harris

The PCM tests the knock system at startup. To see if this is the problem: clear codes, start engine, turn off engine, check for codes. If you have a code 43 it means the knock sensor or ESC (Electronic Spark Control) is not working.

I think the ESC function was moved into the PCM around 1990. Do you have an external ESC module? Does your MEMCAL have an ESC module? Maybe a better question to ask is: did your original MEMCAL have an ESC module and does the new one not have it?

For reference, this is what an external ESC module looks like:



The part on the left is the ESC module incorporated into the MEMCAL (you should be able to see it through one of the holes in the blue cover):

cypher85

Yes it is in the ecm. I can see it on the prom. Hard to find replacements.

Cliff Harris

Why would you need a replacement if you haven't determined that it is bad? Do the test I described earlier.

MrWillys

The ESC is on the memcal in your 1990, and if PCM for less provided you with a tune most likely it came with a piggyback adapter, and not a memcal replacement, so your original ESC is being used? See here to test said circuit:

http://www.chevythunder.com/esc_map_code_43.htm

cypher85

Sorry Cliff I should have said that the test you described was the first thing I did before replacing the knock sensor and checking the wiring. After I replaced the knock sensor I cleared the codes and 43 popped up again.

cypher85

Excellent, thank you for the link. I will do the test and see what happens. I have already checked voltage, it is at 4.97. Have not checked ohms though.

MrWillys

Did PCM for less provide a memcal, or adapter? It is really rare for the ESC unit on the memcal to go bad.

cypher85

No they just provided an adapter.

MrWillys

Can you shoot a pic of the top of the memcal itself?

cypher85

I am not with the car right now. I'll see if can get a picture tomorrow.

cypher85

Here ya go

MrWillys

on top of the ESC unit in red? Is that 2R9290?

cypher85

No it is not red

MrWillys

I'm asking for the code on top of the esc unit in the bluish rectangle?