Newbie needs help with code 43
04-15-2006, 10:18 PM
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Car: 1991 Pontiac Firebird
Engine: 305 V8 TBI
Transmission: stock
Axle/Gears: stock
Newbie needs help with code 43
Hey, everybody, I'm new and looking for guidance.
I have a 1991 Pontiac Firebird with the 305 V8 TBI motor (code E). I am getting code 43 (low voltage at electronic spark timing circuit, or functional test failure). I've gone through Haynes and my recently purchased GM service manual. I've bought a new ESC module, new ECM computer (old PROM), and now 2 knock sensors to try to solve this problem. Continuity in the wiring appears OK. When the car first starts, it runs great for about 5 minutes, then upon heavy acceleration/hill climbing, there is hesitation and the SES light comes on (code 43). The car runs bad (hesitation, uneven idle, very sluggish) until I shut off the ignition, wait a few seconds, then restart (then the problem repeats). Short of going to the dealer, what else could I try?
Thanks, Kevin.
I have a 1991 Pontiac Firebird with the 305 V8 TBI motor (code E). I am getting code 43 (low voltage at electronic spark timing circuit, or functional test failure). I've gone through Haynes and my recently purchased GM service manual. I've bought a new ESC module, new ECM computer (old PROM), and now 2 knock sensors to try to solve this problem. Continuity in the wiring appears OK. When the car first starts, it runs great for about 5 minutes, then upon heavy acceleration/hill climbing, there is hesitation and the SES light comes on (code 43). The car runs bad (hesitation, uneven idle, very sluggish) until I shut off the ignition, wait a few seconds, then restart (then the problem repeats). Short of going to the dealer, what else could I try?
Thanks, Kevin.
Last edited by kasullivan; 04-16-2006 at 10:01 AM.
04-16-2006, 11:33 AM
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Engine: check
Transmission: check
First thing to do is to test the knock system. If the ECM isn't seeing knock from the system then it will error on code 43. If you have a scan tool it makes it much easier to do this. You can then just look for knock counts.
On a warm engine, bring the idle up to about 1000 RPM, and rap on the passenger side of the block. The engine RPM should drop a little then come back up, and the scan tool reported knock counts should increase.
If not, then the knock system is faulty.
If the above test is OK, listen for knock the next time you take it WOT. If you can't hear any then the knock system isn't going to report it either. It may be from too high an octane fuel, too low of timing, or just a detonation resistent engine.
RBob.
On a warm engine, bring the idle up to about 1000 RPM, and rap on the passenger side of the block. The engine RPM should drop a little then come back up, and the scan tool reported knock counts should increase.
If not, then the knock system is faulty.
If the above test is OK, listen for knock the next time you take it WOT. If you can't hear any then the knock system isn't going to report it either. It may be from too high an octane fuel, too low of timing, or just a detonation resistent engine.
RBob.
04-19-2006, 08:29 PM
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Car: 1991 Pontiac Firebird
Engine: 305 V8 TBI
Transmission: stock
Axle/Gears: stock
Scanners: best value for money?
RBob,
Thank you for the advice. I'm willing to spend the money on a scanner, but I want the best value I can get. Ideally, I would like one scanner for all my cars (all GM: '88 Cad, '00 Olds, and of course what brought me here, my '91 Firebird). I know this means having an ODB-I and ODB-II compatible scanner. Can you please give me advice on which one(s) are good values?
Thanks again,
kasullivan
Thank you for the advice. I'm willing to spend the money on a scanner, but I want the best value I can get. Ideally, I would like one scanner for all my cars (all GM: '88 Cad, '00 Olds, and of course what brought me here, my '91 Firebird). I know this means having an ODB-I and ODB-II compatible scanner. Can you please give me advice on which one(s) are good values?
Thanks again,
kasullivan
04-20-2006, 07:50 AM
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Car: check
Engine: check
Transmission: check
For the Firebird if you have a laptop the WinALDL program is free. Will need to make or purchase an ALDL to serial cable for it.
-
I don't have any recommendations for an ODB2 scanner.
RBob.
-
I don't have any recommendations for an ODB2 scanner.
RBob.
04-26-2006, 10:22 PM
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Car: 1991 Pontiac Firebird
Engine: 305 V8 TBI
Transmission: stock
Axle/Gears: stock
Rbob, you are the man!
Who would have thought that having too HIGH of octane would be bad, but you were right! I had been running 93 octane in the Firebird since the engine was rebuilt (1000 miles ago), thinking that would good for my investment. However, that's also about the time I started getting the code 43. Replaced everything the books told me to (knock sensor, ECM, ESC module) and then some (rotor, plugs, wires) and still had problem. Read your post about octane, filled it up with "cheap" 
87 octane, and Voila! No more hesitation or code 43, and the Firebird now runs great! THANKS AGAIN!!
87 octane, and Voila! No more hesitation or code 43, and the Firebird now runs great! THANKS AGAIN!! 
06-23-2014, 12:35 PM
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Re: Newbie needs help with code 43
Hi friends..
i have exact the same problem.. but we don't have fuel with less than 95 octane.. we changed almost everything possible.. :-( nothing works.. i am from switzerland, but i try to list up all the things we tested or changed:
- Spark Plugs (2 sets of ACDelco UR4 and 1 set NGK UR4)
- Ignition coil
- Ignition Control Module (ICM)
- Electronic Computer Module (ECM)
- Distributor
- Distributor Cap
- Spark Plug Wires
- Engine Ground Cable
- O2 Sensor
- MAP Sensor
- Knock Sensor
- Alternator
- ESC Module
- and checked a lot of cables..
Story about: Replaced the L03 engine with a brandnew l03.. was driving 200 miles..
than i got a "Check Engine" lamp.. Error 43.. motor off, motor on and its gone.. for 4-6 miles.. this problem we have now 3 months..
does anybode had the same problem and the solution for it? Help!!! :-(
i have exact the same problem.. but we don't have fuel with less than 95 octane.. we changed almost everything possible.. :-( nothing works.. i am from switzerland, but i try to list up all the things we tested or changed:
- Spark Plugs (2 sets of ACDelco UR4 and 1 set NGK UR4)
- Ignition coil
- Ignition Control Module (ICM)
- Electronic Computer Module (ECM)
- Distributor
- Distributor Cap
- Spark Plug Wires
- Engine Ground Cable
- O2 Sensor
- MAP Sensor
- Knock Sensor
- Alternator
- ESC Module
- and checked a lot of cables..
Story about: Replaced the L03 engine with a brandnew l03.. was driving 200 miles..
than i got a "Check Engine" lamp.. Error 43.. motor off, motor on and its gone.. for 4-6 miles.. this problem we have now 3 months..
does anybode had the same problem and the solution for it? Help!!! :-(
Last edited by transamch; 06-23-2014 at 02:09 PM.
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06-23-2014, 05:30 PM
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Re: Newbie needs help with code 43
If this occurs under heavy throttle it is the forced knock test failing. Same as the original poster. As far as having 95 octane as the lowest available, I think that Europe rates their octane differently then the US.
Which makes the rating higher then it is here.
First thing is to test the ESC system. If it works, check the base spark timing. Stock is at TDC (0*), if that is where it is then bump it 2* to 4* BTDC. That may be enough to get the engine to knock.
A search on this board and the TBI board here with "forced + knock" and my name as the author will bring up others threads discussing this issue.
RBob.
Which makes the rating higher then it is here.
First thing is to test the ESC system. If it works, check the base spark timing. Stock is at TDC (0*), if that is where it is then bump it 2* to 4* BTDC. That may be enough to get the engine to knock.
A search on this board and the TBI board here with "forced + knock" and my name as the author will bring up others threads discussing this issue.
RBob.
09-05-2018, 08:51 PM
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Car: 89 IROC Convertible
Engine: 305
Transmission: auto
Re: Newbie needs help with code 43
I have an 89 305 TPI automatic convertible running Shell premium (91 or 93 octane I can't remember) and experienced the persistent code 43 after changing my engine coolant. Part of the coolant change requires removal of the knock sensor because it serves as the drain plug on the passenger side too. All the testing I did showed up as no problem, yet every time I enthusiastically accelerated to get on the highway, severe loss of power (due to spark retard), and check engine light ( always code 43) was the result. I thought I had overtorqued the sensor or perhaps it was because I put a wrap of teflon tape on it during reinstall. Nope, the service manual calls for sealant tape and I actually reduced the torque to 13.5 ftlb to account for torque wrench tolerance. No change. Then I rerouted the single conductor to the sensor around the ribbed metal brake line near it to hold it away from the spark plug wires and bent the bracket (very soft metal) down so the wire bundle containing the knock sensor wire was as far from the spark wires as possible. Success, no code 43. I assume that I miss routed the sensor wire when I disconnected it to remove the sensor for coolant replacement.
04-06-2019, 08:13 PM
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Car: 89 IROC Convertible
Engine: 305
Transmission: auto
Re: Newbie needs help with code 43
Update to code 43. Started getting code 43 again, ugh! Replaced the knock sensor, no change. Got the idea to check the timing, holy cow, found it retarded past the edge of the degree indicator scale. Reset the timing to 6 deg btdc and no code 43. This was probably my problem all along. Must have been failing the “forced knock test” . By the way, the distributor locking bolt needs 15mm wrench.
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