Knock sensor riddle
04-26-2016, 10:28 AM
#1
Staging Lane
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Knock sensor riddle Got a 99 GMC rcsb 5.3 bored to 5.7 PRC heads vinchi cam etc I have knock sensor codes po327 and po332 I have replaced the sensors and harness 4 times no change has a perfect 99 ohms coming through the harness duno what the deal is unless it's a ground issue I dont have any blueprints of that circuit though we cleared it before tuning it stayed off the whole time then came bak on on way home in overdrive it definitely pulls timing hard engine is super smooth no idea what is going on I've seen the same problem online but never a fix any answers or suggestions Are welcome
04-26-2016, 12:29 PM
#3
Staging Lane
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Every time I try to get a tuner to disable them they either don't respond to me or don't wana do it the engine I built very conservative I would be plenty fine with turning them off just got no one to do it
04-26-2016, 01:22 PM
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Staging Lane
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Thanks exactly what I was looking for I thought they did just wanted to make sure I'm gona start checking out the PCM connection I guess I saw alot of people replacing the PCM and didn't fix the problem I'm not gona replace it I guess I'll see if I'm getting the proper reading there if I can figure out where to test at.
04-26-2016, 05:19 PM
#6
CIRCUIT DESCRIPTION
The Knock Sensor (KS) system detects engine pre-detonation. The Powertrain Control Module (PCM) retards the spark timing based on the signals from the knock sensors. The knock sensors produce an AC voltage when specific frequencies are detected. The knock sensor voltages are an input to the PCM. The amount of AC voltage produced is proportional to the intensity of the knock.
An operating engine produces a normal amount of engine mechanical vibration. The knock sensors produce an AC voltage signal from this noise. When an engine operates, the PCM learns the minimum and maximum frequency of the noise that the engine produces. When the PCM determines that this frequency is less than or more than the expected amount, a knock sensor Diagnostic Trouble Code (DTC) sets.
CONDITIONS FOR RUNNING THE DTC
The engine speed is between 1,500 RPM and 3,000 RPM .
The MAP is less than 44 kpa .
The Engine Coolant Temperature (ECT) is more than 60°C (140°F) .
The throttle angle is more than 0.5 percent .
The engine run time is more than 20 seconds .
CONDITIONS FOR SETTING THE DTC
The PCM determines that this frequency is less than or more than the expected amount for less than 3 seconds .
The Knock Sensor (KS) system detects engine pre-detonation. The Powertrain Control Module (PCM) retards the spark timing based on the signals from the knock sensors. The knock sensors produce an AC voltage when specific frequencies are detected. The knock sensor voltages are an input to the PCM. The amount of AC voltage produced is proportional to the intensity of the knock.
An operating engine produces a normal amount of engine mechanical vibration. The knock sensors produce an AC voltage signal from this noise. When an engine operates, the PCM learns the minimum and maximum frequency of the noise that the engine produces. When the PCM determines that this frequency is less than or more than the expected amount, a knock sensor Diagnostic Trouble Code (DTC) sets.
CONDITIONS FOR RUNNING THE DTC
The engine speed is between 1,500 RPM and 3,000 RPM .
The MAP is less than 44 kpa .
The Engine Coolant Temperature (ECT) is more than 60°C (140°F) .
The throttle angle is more than 0.5 percent .
The engine run time is more than 20 seconds .
CONDITIONS FOR SETTING THE DTC
The PCM determines that this frequency is less than or more than the expected amount for less than 3 seconds .