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What problems would no Knock Module cause?


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#1 caner_saka

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Posted A week ago

I've been trying to diagnose my 95 formulas problems and found I had no knock module in the ecu. What sort of things would this cause?



#2 Injuneer

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Posted A week ago

You determined this by opening the cover for the knock module, or from a DTC code?  PCM should have set DTC 47 for a missing knock module.

 

First time in 20+ years helping people with the LT1 I seen this question asked., and no idea what problems it might cause.  The 1995 factory service manual does not include the info regarding “action taken” or whether it turns on SES light when the code is set.  The 1996 manual indicates the corresponding OBD-2 code does not turn on the light.  When the knock sensor (not the module)  has a fault, the PCM defaults to retarding the ignition timing based on engine load, throttle position, etc.  That means you are seeing reduced power most of the time.

 

Should be relatively easy to find a used replacement.  Many people have replaced the LT1 knock module with an LT4 knock module, in the belief it will improve performance.  It may or may not depending on engine modifications, but not much n a stock engine. 

 

http://shbox.com/1/lt4km.jpg
 

 


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#3 caner_saka

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Posted A week ago

You determined this by opening the cover for the knock module, or from a DTC code?  PCM should have set DTC 47 for a missing knock module.

 

First time in 20+ years helping people with the LT1 I seen this question asked., and no idea what problems it might cause.  The 1995 factory service manual does not include the info regarding “action taken” or whether it turns on SES light when the code is set.  The 1996 manual indicates the corresponding OBD-2 code does not turn on the light.  When the knock sensor (not the module)  has a fault, the PCM defaults to retarding the ignition timing based on engine load, throttle position, etc.  That means you are seeing reduced power most of the time.

 

Should be relatively easy to find a used replacement.  Many people have replaced the LT1 knock module with an LT4 knock module, in the belief it will improve performance.  It may or may not depending on engine modifications, but not much n a stock engine. 

 

http://shbox.com/1/lt4km.jpg
 

 

I opened the cover and found it missing but it's because I recently got a replacement PCM. So far I haven't found a scanner that works for 95 so I don't know what my problem is. I did a security bypass with a module but security light won't go off which I was guessing was because I needed to reprogram the PCM but it didn't work. I was hoping the missing knock module could be causing this.



#4 caner_saka

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Posted A week ago

Which also brings up my next question, I have a VATS bypass module from timers.shop that is apparently supposed to work with this car. Should this rule out any problems in my security?



#5 sea dog

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Posted A week ago

It depends on what type of module you bought. They make vats bypass modules that take the place of the chip in the key. They do this by having all 15 chip resistances built into the module. This type of module is good for vats problems relating to worn lock cylinder, or not having the key with correct chip, or no chip at all.

 

The 2nd kind of module has the 50 hertz fuel enable signal that bypasses the Theft deterrent module. The TDM on 94-95 4th gens sends the 50 hertz fuel enable signal to computer. On 93 cars it's a 30 hertz signal. With the bypass module of this type, you eliminate the TDM from the system chain.

 

However, the vats system also has a theft deterrent relay (TDR). The TDR, when vats system is working correctly, enables the starter to operate. Many cars of the age of yours have had the TDR bypassed by a previous owner. If it hasn't been bypassed, you would need to when using the 50 hertz bypass module.

 

You need to go to the shoebox site to read up on the vats security system. http://www.shbox.com

 

Also 95 service manual has info on vats system. http://www.mediafire.../?40mfgeoe4ctti



#6 caner_saka

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Posted A week ago

It depends on what type of module you bought. They make vats bypass modules that take the place of the chip in the key. They do this by having all 15 chip resistances built into the module. This type of module is good for vats problems relating to worn lock cylinder, or not having the key with correct chip, or no chip at all.

 

The 2nd kind of module has the 50 hertz fuel enable signal that bypasses the Theft deterrent module. The TDM on 93-95 4th gens sends the 50 hertz fuel enable signal to computer. With the bypass module of this type, you eliminate the TDM from the system chain.

 

However, the vats system also has a theft deterrent relay (TDR). The TDR, when vats system is working correctly, enables the starter to operate. Many cars of the age of yours have had the TDR bypassed by a previous owner. If it hasn;t been bypassed, you would need to when using the 50 hertz bypass module.

 

You need to go to the shoebox site to read up on the vats security system. www.shbox.com

 

Also 95 service manual has info on vats system. www.mediafire.com/?50mfgeoe4ctti

The module I have is a 50 hertz signal one. With that would the key value matter? There was one resistor in my wires and all that. How would I bypass the TDR if all I'm bypassing is the TDM?



#7 Injuneer

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Posted A week ago

Knock module and PCM program have nothing to do with the PASS-Key (VATS) system, or turning on the SECURITY light.

 

Did you read and follow up with the link I gave you in post #2 in this thread:

 

https://www.firebird...and-wont-start/

 

The possible culprits are the key, key cylinder, theft deterrent relay, theft deterrent module, and the wiring between them.

 

To clarify:

 

- is the SECURITY light on solid, or flashing?

 

- when you turn the key to START, does the starter engage and crank the engine?

 

- if the starter cranks the engine, does it show any signs of firing, sputtering, popping, etc?



#8 caner_saka

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Posted A week ago

The reason I asked about PCM is because when I bought it the seller stated steps to reprogram in order to turn the security light off. The light is solid and the engine cranks, but it cranks consistently, unless something like starter fluid is used, the bypass module doesn't seem to change anything.


Edited by caner_saka, A week ago.


#9 Injuneer

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Posted A week ago

The SECURITY light is turned on and off by the theft deterrent module.  The PCM does not control it or cause it to light up.

 

http://shbox.com/1/pass_key.jpg

 

Have you checked the continuity of the dark blue wire that connects the 50Hz module to pin A25 of the PCM? Have you checked the pin and corresponding socket in the PCM connector for damage?

 

Any real OBD-1 scanner  will work on your 1995.  You just need a 12-pin to 16-pin adapter, or jumper wires:

 

http://shbox.com/1/xraycable.jpg
 

”Code scanners” like the Actron 9001, which is simply a box that shorts the ALDL pins will not work.



#10 caner_saka

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Posted A week ago

I'll work on getting an OBD 1 scanner thank you for all the clarifications so far.



#11 sea dog

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Posted A week ago

When you hooked up the 50 hertz bypass module up, did you make sure you hooked the signal wire to the correct dark blue wire going into the pcm? The pcm connectors contain several dark blue wires.

 

THe pcm connector that fuel enable signal goes to is the red A connector. Cavity 25. That red connector has 2 other dark blue wires going into it. So a novice could connect the signal wire of 50 hertz module to wrong wire.

 

The module also has a ground wire that needs to go to a good ground. And a power wire that needs to be connected to key on only power source.

 

Also, the module could be defective. The only 100% way to check the output signal of module is with an oscilloscope. Output should be a 2.5 volt square wave.



#12 caner_saka

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Posted A week ago

I definitely had the right location in the PCM, however I had the power hooked up straight to the battery's power and ground. Would it being a key on only power source change anything?



#13 sea dog

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Posted A week ago

Having module hooked up to a key on power source would keep it from running all the time. After all, the signal from module is only needed when cranking engine and engine is running.



#14 caner_saka

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Posted A week ago

Just to clarify should that 50 hz signal go to the pcm, out the pcm, or just be in line of the dark blue wire? And if the 50 hz signal does work when checked with an oscilloscope that would most likely mean my problem exists elsewhere right?



#15 sea dog

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Posted A week ago

The dark blue fuel enable wire to PCM connector A( the red one), cavity 25 goes to PCM. The usual way of connecting the module is to cut the dark blue wire several inches from PCM. You then hook the signal wire from module to the end of cut wire from PCM.

 

If you simply spiced the module wire into the dark blue wire, there is the possibility of having signal from TDM and your module going to PCM.  Which would cause trouble.

 

So you say that security light was on all the time. It didn't keep starter from working, does your engine run with security light on?

 

Besides security system, codes 16, 41, & 42 will keep your engine from running. And all 3 codes don't light the check engine or service engine light, depending on which one 95 has. Code 16 is opti low resolution pulse missing. 41 & 42 are both icm codes. Read up on them in 95 service manual. It gives chapter & verse on each code.

 

These codes and other codes that don't light the CEL, are some of the reasons you need an obd 1 scanner.






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