New to this so, please bear with me... I need some help or advice please!!

I recently replaced the OBDII ecm in my 96Z with an OBDI ecm from a 95 LT1 Buick Roadmaster. The fellow helping me, used the Tunercat software to tune the OBDI ecm. The problem that I need help and or advice with is the code 43 that it's throwing. I changed the knock module in the ecm to a LT4 module but, it did not help. Can I or should I install a 95 knock sensor? Will it be compatible with the wiring harness in my 96? Or, am I heading in the wrong direction? Please point the way...

Thanks!

 

Here's a list of codes from totse.com
-------------------------------------

CODES USED BY COMPUTERS IN GM CARS

New cars use computers to store and remember malfunctions that occur.
These are displayed in the flashing sequences in the instrument cluster. A
typical sequence of instructions follows:

Locate the C3 diagnostic connector (also called the "ALCL"). It is usually
under the dash on the drivers side. On the Ponitac Fiero, however, it is
located in the console between the seats. Short the 'A' & 'B' positions of
the diagnostic conector ('B' is ground), then turn the ignition key on but do
not start the engine.
CHECK ENGINE OR SERVICE ENGINE SOON light on dash will flash out the
number 12 ( flash - pause - flash flash ) which means the self diagnostic
mode is working. This will be repeated 3 times. Any trouble codes the
computer (called the Electronic Control Module or ECM) has stored will then
be flashed out ( for example: code 23 is ( flash flash - pause - flash flash
flash ). If more then one code has been stored, they will be flashed out in
order, each repeated 3 times. Look up the code in the following chart to
find the faulty circuit or component.

NOTE: Do not automatically replace a component without first checking its
wiring and connectors. Also, it is good practice to test the component
further using a digital volt/ohm meter as described in the vehicle's service
manual. Remove the A to B short and turn off the ignition. After the
repairs, clear the trouble codes from the computor's memory by disconnecting
the fuse marked 'ECM' for at least 10 seconds.

C3 TROUBLE CODES

12- Normal code with ignition on and engine off. Indicates
no distributor reference pulse to ECM. Not stored in
memory.
13- Oxygen sensor or it circuit
14- Coolant Temperature Sensor circuit shorted.
15- Coolant Temperature Sensor circuit open.
21- Throttle Position Sensor (TPS) or its circuit.
22- Throttle Position Sensor circuit voltage low due
to grounded circuit or faulty adjustment of TPS.
23- Mixture Control (MC) Solenoid circuit open or
grounded.
24- Vehicle Speed Sensor (VSS) or its circuit
32- Baromteric Pressure Sensor circuit voltage low.
34- Vacuum Sensor or Manifold Absolute Pressure (MAP) circuit.
35- Idle Speed Control (SC) Switch circuit shorted.
41- No distributor reference pulse to the ECM. Unlike code 12,
this will be stored in the ECM.
42- Electronic Spark Timing (EST) bypass circuit, or EST
circuit open or grounded.
43- Electronic Spark Control retard signal for too long
a time.
44- Lean exhaust
45- Rich exhaust
51- Prom (programmed read only memory) calibration unit faulty
or improperly installed in ECM.
53- Exhaust Gas Recirculation (EGR) valve vacuum sensor
has received improper vacuum signal.
54- Shorted Mixture Control Solenoid circuit and/or
faulty ECM.
55- Grounded Vref (terminal 21), high Oxygen Sensor circuit
sensor voltage, or faulty ECM.

Hope this helps!

Fred

 

Note the following regarding the conditioning module:
(From Mega-Squirt website)

The knock sensor is tuned to a specify frequency, like a tuning fork. When this frequency is applied to the sensor (through its connection to the engine), a piezoelectric crystal inside the sensor generates a small voltage (~1 volt), much like a microphone.

As an example, some Corvette knock sensors (GM PN 1997562, 1997699, OR Standard Motor Products KS45, KS46, KS49, or KS117) have a design frequency of 5200 hertz, and they produce a signal between 4800 rpm and 5600 rpm.

On the Corvette L83/L98/LT1/LT4 engines, this sensor is usually screwed (with a specified torque value) into the coolant drain hole near the center of the block side, just above the oil pan rail. This location has been chosen as optimum for this sensor and engine family. On the LS1 engine, the sensors (there are two) are located in the center valley on top of the engine
A conditioning module is also required, such as GM's Electronic Spark Control (ESC) module (PN 16022621, 16052401), see above. These are also available as Standard Motor Products LXE6, LXE7, and LXE9. These are very common in recycling yards, they were used all virtually all GM vehicles from the mid-1980s to the late 1990s.

A conditioning module is also required, such as GM's Electronic Spark Control (ESC) module (PN 16022621, 16052401), see above. These are also available as Standard Motor Products LXE6, LXE7, and LXE9. These are very common in recycling yards, they were used all virtually all GM vehicles from the mid-1980s to the late 1990s. You should match the sensor and module by application to ensure they will work together properly.
Threshold (V): The is the voltage from the knock sensor module which defines whether there is knock occurring or not. Note that you can define a 6-element table of rpm versus voltage instead of a single value. You define this table under 'Settings/Knock Threshold'. The GM sensor/module signal is ON/OFF, but the knock threshold value/table is there in case someone has a system they can calibrate to their car by a threshold.
Peak (V): the maximum expected voltage value on the knock signal, used in some configurations where the difference between the signal level and the maximum levels indicates the degree of knocking.
Knock Count (knocks): number knock detects required for valid detection
No Knock Above MAP (kPa): no knock retard is implemented above this MAP
No Knock Below RPM (rpm): no knock retard is implemented below this rpm
No Knock Above RPM (rpm): no knock retard is implemented above this rpm, which may be desirable if valve train noise triggers the knock sensor when knock isn't actually occurring.
Maximum Retard (deg): maximum total retard when knock occurs. This can be useful to prevent timing from being excessively retarded (avoiding potential overheating issues) if the senor malfunctions or there are other problems with the knock sensing system.
Retard Check Time (sec): this is the time between knock retard corrections, allows short time step to quickly retard
Retard Step Size (deg): ignition retard step size when 1st knock or after stopped, make it large to quickly retard the timing and stop knock
Advance Check Time (sec): this is the time between knock advance correction (I.e., timing return to 'normal')
Advance Step Size (deg): ignition advance steps after knock has stopped
Recovery Advance (deg)): this is the change in table advance required to restart advance until knock or reach table value (0 knock retard) process. This only applies in 'Safe Mode' .

Verify your parts and that they are compatible with each other. I would start there.

Good Luck!

Fred

 

If you change from an OBD-II computer to an OBD-I, you must change the knock sensor, too. It's as simple as that. They are different impedances and cannot be interchanged.

 

Should I have any concerns with matching the new replacement ESC and wiring connection compatibility? Havent yet got to that point (under the car), just trying to be prepared and anticipate what's ahead...

Thank you one and all for the help and info.

 

I agree. As a side note, I posted the information so he could learn what is going on here. He said he was new to this, and I remember what that was like!

Fred

 

It's a bit overwhelming... what can be done with these computer controlled cars. ...and how easy it is to get into trouble not knowing what to anticipate.

Thanks everyone that took the time to post and help me out!

W

 

Is the electronic spark control module the same thing as the knock module? I had that code and could never get rid of it. The voltage and resistance (after replacing the KS) checked out, but the SES stayed on. Just clarifying what the electronic spark control module is.

 

ESC was used in the 3rd Gen engines, and referenced in their diagnostics. It is not a term used for the 4th Gen LT1's.

For the Gen 4 OBD-I LT1, DTC 43 = Knock Sensor (KS) circuit (not what is written in the posts above). You have to use a code list that is SPECIFIC to the engine you are working on. Unfortunately many scanners include generic code lists that will often point you in the wrong direction. There is also DTC =47 Knock Sensor (KS) module circuit or module missing... again, no reference to "ESC".

The DTC 43 diagnostic is very simple... it looks at the voltage on the circuit, and sets the code if it goes above 3.5V or below 1.5V. It has nothing to do with "retard signal for too long". The OBD-II (96/97) knock sensor has a resistance of 100Kohms. Its going to give you the wrong circuit voltage when attached to an OBD-I PCM, that is expecting the circuit to respond to the 4.4Kohm sensor used in the 93-95 LT1's.

Do NOT use a generic list like the one posted above, unless you have no other possible source. For an LT1, use the specific list the Shoebox has posted on his website. It is 100% accurate.

http://shbox.com/1/Dtcs.htm

 

There is an internal modification that can be done to make an OBDI PCM compatable with an OBDII knock sensor. PCMforless and MadZ28 do this... and that's what has been done with mine.

But probably an easier solution for you is what has already been suggested by others here - replace the knock sensor with an OBDI unit.