Very confused (code 43)

This one really confuses me. OK, I reset the ECM, clear the code..... leave my scan tool in the ALDL and about 2 minutes into driving (not at idle) the CEL pops (code 43) and the car is really sluggish. I stomp the gas a few times, CEL goes away but code 43 sticks. After the light goes off (still have scan tool plugged in) the car is the fastest thing I have rode in.. Shut the car off, pull the scan tool, BOOM, the performance sucks again, and code 43 sticks, but no CEL....... Any clues as to why having the scan tool plugged in makes a difference, or anyone know what might cause this? BTW code 43 is for ESC failure. Timing is set pretty good, about 6-8 BTDC. I am lost..

This one really confuses me. OK, I reset the ECM, clear the code..... leave my scan tool in the ALDL and about 2 minutes into driving (not at idle) the CEL pops (code 43) and the car is really sluggish. I stomp the gas a few times, CEL goes away but code 43 sticks. After the light goes off (still have scan tool plugged in) the car is the fastest thing I have rode in.. Shut the car off, pull the scan tool, BOOM, the performance sucks again, and code 43 sticks, but no CEL....... Any clues as to why having the scan tool plugged in makes a difference, or anyone know what might cause this? BTW code 43 is for ESC failure. Timing is set pretty good, about 6-8 BTDC. I am lost..

Scan tool pluged in may be over riding the pcm and holding it in base test/check mode.
Anything from Knock sensor to esc module or wiring. First thing to check would be if knock sensor is pluged in good.
Your best bet is some real good repair info like factory service manual or a DIY all data online repair info sub.
http://www.alldata.com/products/diy/index.html
Get the repair flow chart for code 43 for your car and engine and go threw it.
Let us know how it goes.
MT

Actually I went through the repair chart listed in my Howell TPI manual. Knock sensor and ESC mod. are both brand new. I dunno.... can't figure out why it works ok with the scanner in but only AFTER the CEL comes on and then goes off.

Actually I went through the repair chart listed in my Howell TPI manual. Knock sensor and ESC mod. are both brand new. I dunno.... can't figure out why it works ok with the scanner in but only AFTER the CEL comes on and then goes off.

What year make and model and engine and engine code?
What is the prom scanner id no?
MT

It's an 85 IROC but I just got done putting in the 350. Has the TPI setup on it. Custom PROM. I think it's 7714 or 7741 PROM, not sure... I don't think any of that info is useful, haha.

Just because the parts are new does not mean they are not defective....

Just because the parts are new does not mean they are not defective....

True, but I have never had a Delco part be bad before when it was new. I wish I knew what exactly happens to the computer when you hook a scan tool to it. I know when I scan and check data it brings the revs up, but not sure on the technical aspect.

It's an 85 IROC but I just got done putting in the 350. Has the TPI setup on it. Custom PROM. I think it's 7714 or 7741 PROM, not sure... I don't think any of that info is useful, haha.

It do make a differance.
Do you have the prom that came out of it to try back in it?
Is the computer for a V8 or was it for a different engine?
Do you have the ecm no and the prom id no.? I do not find a 7714 0r 7741 listed.
Do not worry about it running different with scanner on it.
When a scanner is pluged in or you jumper a and b it puts the ecm it in a different test mode.
Even my old snappy MT-2500 has 2 modes when you plug it in.
For the code run your voltage test and check wiring real close. You should see about 6 volts to the ecm and a change in voltage if you tap engine to similate knock.
I can e mail you a flow chart and test for that code if it would help.
Drop me a e mail at [email protected] if you need it.
Good luck
MT

About the high RPM with the ALDL cable plugged in. What's happening is there is a 10k resistor on your diagnostic tool which sets off diagnostic mode, or ALDL mode. This mode does a lot of different things, but mainly it activates all the little stuff on your car that could throw a code so it knows what's working and what's not. This includes the IAC (Idle Air Control) with helps control idle speed, which is why you get a higher idle.

Since you have an 85, I'm assuming that you replaced a 305 with the 350. Here's a list of what I would check.

1. Knock sensor. If you still have the stock KS or KS for a 305, you need to replace it with a 350 KS. With a 305 KS you will get A LOT more knock counts than you should and the ECU will pull timing like crazy.

2. ESC connector. Especially after you set your timing, you should double check that the ESC is totally hooked back up. Make sure that the little plastic clip is completely over top of the notch on the connector.

3. Wiring from ESC module. Check you wiring and make sure that you don't have a bad wire coming from the ESC.

4. ESC module. If any of that doesn't help, I think it'd be safe to say that your ESC module is going bad.

True, but I have never had a Delco part be bad before when it was new. I wish I knew what exactly happens to the computer when you hook a scan tool to it. I know when I scan and check data it brings the revs up, but not sure on the technical aspect.


One that one you are not supposed to drive it with scan tool plugged in unless the scan tool has a road test mode.

If you clear codes and leave the scan tool off will it run right or does it just act up after you plugin scan tool?
MT

One that one you are not supposed to drive it with scan tool plugged in unless the scan tool has a road test mode.

If you clear codes and leave the scan tool off will it run right or does it just act up after you plugin scan tool?
MT

Unsure, but I will give it a try. I don't believe that it makes a difference. Oh yeah, all the sensors are for the 350, and they are all new. The computer is original from the car it had a 305 TPI. Putting the old chip in is not a good idea. It ran very badly. Could not even move the car. Right now this is the only problem I have with the car. Otherwise completely drivable.

It's an 85 IROC but I just got done putting in the 350. Has the TPI setup on it. Custom PROM. I think it's 7714 or 7741 PROM, not sure... I don't think any of that info is useful, haha.
If you have a 350 in the car now you MUST have a knock sensor for a 350. There is a big difference between the 350 and 305 knock sensors. Some people also say you have to use the ESC module from a 350 too but I've found that one to be untrue.
I can tell you from exprience that if you use a 305 knock sensor in a 350 you will get a code 43, no ifs, ands or buts, it will set that code.

If you have a 350 in the car now you MUST have a knock sensor for a 350. There is a big difference between the 350 and 305 knock sensors. Some people also say you have to use the ESC module from a 350 too but I've found that one to be untrue.
I can tell you from exprience that if you use a 305 knock sensor in a 350 you will get a code 43, no ifs, ands or buts, it will set that code.

Every sensor on the car is new and is for a 350 TPI setup. Also the ESC module is from the 350 TPI and is brand new too. Actually, everything but the alt, the ps pump and the intake is new, including the motor. Glad to see you posting on this though Morley, as you have done the swap that I have done in the same year/model of car.

Try putting the old ESC module back in the car and see if that cures it. 1985 was a unique setup and I'm not sure if the Corvette's ESC (only 1985 350 TPI around) will work correctly with the 305's wiring harness, they wern't pinned exactly the same.
Also, have you looked into doing the 165 ECM swap? It is a very easy job and gets you out of the 870 ECM with all of its quirks and uniqueness.

The sensor and module may be new and dandy. How is the wiring, are you sure you didn't bake the wire off the sensor? Can you see the knock counts and timing on the scanner?

The sensor and module may be new and dandy. How is the wiring, are you sure you didn't bake the wire off the sensor? Can you see the knock counts and timing on the scanner?

Wiring is good. Sadly this old ECM does not show knock counts or timing.

Try putting the old ESC module back in the car and see if that cures it. 1985 was a unique setup and I'm not sure if the Corvette's ESC (only 1985 350 TPI around) will work correctly with the 305's wiring harness, they wern't pinned exactly the same.
Also, have you looked into doing the 165 ECM swap? It is a very easy job and gets you out of the 870 ECM with all of its quirks and uniqueness.

I'll give that a shot when the weather gets nicer around here. I'll post again letting you guys know what I all tried and if any of it worked.