P0325/P0332 diagnosis
10-02-2019, 08:44 AM
#1
Launching!
Thread Starter
P0325/P0332 diagnosis Trying to diagnose low voltage on both knock sensors . Knock sensors replaced with harness 2500 miles prior with gm units Both read 99k resistance but only getting .01to.09 ac volts when simulating knock. Does anyone definitively know if there should be a bias voltage produced by the pcm? Harness connections all test ok with continuity back to pcm. GM pcm # 12200411in a conversion.5.3 liter truck motor from a 02 Silverado.I know this is a common issue and have searched the web,but no definite answers as to whether the pcm generates a 5 volt bias voltage or not. Key on engine running,I show 0 volts on either line to the sensors from the pcm. Any suggestions appreciated.
10-04-2019, 12:38 AM
#2
Trying to diagnose low voltage on both knock sensors . Knock sensors replaced with harness 2500 miles prior with gm units Both read 99k resistance but only getting .01to.09 ac volts when simulating knock. Does anyone definitively know if there should be a bias voltage produced by the pcm? Harness connections all test ok with continuity back to pcm. GM pcm # 12200411in a conversion.5.3 liter truck motor from a 02 Silverado.I know this is a common issue and have searched the web,but no definite answers as to whether the pcm generates a 5 volt bias voltage or not. Key on engine running,I show 0 volts on either line to the sensors from the pcm. Any suggestions appreciated.
do you know what OS your 0411 PCM is running?
did you clean up the threads on the mounting bosses and torque the sensors to spec?
it really sounds like the sensors are working as they should. And the wiring appears to be functional. I’m wondering if the sensors are not compatible with your tune...
10-04-2019, 09:43 AM
#3
Launching!
Thread Starter
To answer your questions, I put what I thought were new ac/delco sensors and harness in when I built the engine 2500 miles ago. The operating system is a stock system from an 02 silverado 1500 2wd pickup.The threads were spotless as this is a new build.The sensors were torqued to 15 ft/lbs .I am starting to suspect after removing these sensors that they might be counterfeit ac/delco parts. I ordered 2 new ones and will compare the prior ones with the new ones. Will keep you posted as to what I find.
10-04-2019, 10:07 AM
#4
My 99 Z28 used to throw these codes regularly.
One day I swapped on an LS6 intake, didn't touch the knock sensors, and from that point on, the codes never came back.
I have to imagine it was related to the intake touching or rubbing against something underneath.
One day I swapped on an LS6 intake, didn't touch the knock sensors, and from that point on, the codes never came back.
I have to imagine it was related to the intake touching or rubbing against something underneath.
10-04-2019, 10:49 AM
#5
When you mentioned new GM units I assumed they were from the dealership. But it does sound like your sensors are working. Crazy question but did you clear the OBD2 codes after you replaced them? Or are you still seeing the old stored codes? Otherwise I’m thinking it’s a loose connector or possibly a pinched harness like Mike mentioned.
10-04-2019, 11:05 AM
#6
Launching!
Thread Starter
In response to wire harness being pinched or rubbed through,I have checked it closely and have no evidence of any problems.The sensors were bought online and appeared to be in ac/delco packaging but I am suspicious, as there are more and more fakes out there every day
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10-07-2019, 08:25 PM
#8
This from previous post.....
DTC P0327 Knock Sensor (KS) 1 Circuit
Circuit Description
The Knock Sensor (KS) system detects engine pre-detonation. The 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 (noise). 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 the engine produces. When the PCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set.
Conditions for Running the DTC
• The engine speed is between 1,650 RPM and 3,000 RPM.
• The MAP is more than 49 kPa.
• The engine coolant temperature is more than 60°C (135°F).
• The throttle angle is greater 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.
Action Taken When the DTC Sets
• The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
• The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
• The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
• A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
• Use a scan tool in order to clear the MIL and the DTC.
Diagnostic Aids
Important:
• Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
• For any test that requires probing the PCM or component harness connectors, use the J 35616 connector test adapter kit. Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems.
Inspect the knock sensor for proper installation. A knock sensor that is loose or over torqued may cause the DTC P0327 to set.
For an intermittent, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2 This verifies the malfunction is present. The scan tool will display DTC Ran=Yes and Pass=Int if the failure is intermittent. This indicates the diagnostic passed this ignition cycle and failed this ignition cycle. At this point the resistance of the knock sensors should be verified to be in the correct range. If the knock sensor resistances are correct, inspect the KS system wiring connections. When testing the KS system connections, start at the KS system jumper harness connector located behind the intake manifold. Then inspect the connections at the PCM. Refer to the wiring schematic for the correct connector and terminal. Then inspect the connections at the appropriate knock sensor. Failure Records data does not include the parameter KS Activity, however other parameters may aid in locating the conditions under which an intermittent occurred.
3 This test isolates the Knock Sensor from the rest of the circuit.
4 Tap on the engine block near the appropriate knock sensor. Do not tap on plastic engine components.
Step
Action
Value(s)
Yes
No
1
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?
—
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check
2
Important: If an engine knock can be heard, repair the engine mechanical condition before proceeding with this diagnostic. Refer to Engine Noise Diagnosis in Engine Mechanical.
1. Turn ON the ignition leaving the engine OFF.
2. Review the Freeze Frame and/or Failure Records data for this DTC and observe the parameters.
3. Turn OFF the ignition for 15 seconds.
4. Start the engine.
5. Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in Freeze Frame and/or Failure Records as possible. Special operating conditions that you need to meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running the DTC.
6. Monitor the Diagnostic Trouble Code (DTC) information using a scan tool.
Does the scan tool indicate that this diagnostic failed this ignition?
—
Go to Step 3
Go to Diagnostic Aids
3
1. Disconnect the knock sensor electrical connector located behind the intake manifold.
2. Measure the resistance between the appropriate knock sensor signal circuit (sensor side of harness) and the battery ground using the DMM.
3. Set the DMM to the 400K ohm scale.
Is the resistance of the knock sensor within the specified range?
93–107KΩ
Go to Step 4
Go to Step 6
4
1. Connect the DMM between the appropriate knock sensor signal circuit (sensor side of harness) and the engine block.
2. Set the DMM to the AC voltage scale.
3. Tap on the engine near the appropriate knock sensor while observing the signal indicated on the DMM.
Is any signal indicated on the DMM while tapping on the engine near the appropriate Knock Sensor?
—
Go to Step 5
Go to Step 7
5
1. Disconnect the PCM connector C1 located on the same side as the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
2. Test the KS signal circuit between the PCM and the knock sensor connector for the following:
• An open
• A short to voltage
• A short to ground
3. If you find a condition repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
—
Go to Step 10
Go to Step 8
6
1. Remove the intake manifold. Refer to Intake Manifold Replacement in Engine Mechanical–5.7L.
2. Test for an open or a short to ground in the signal circuit between the knock sensor jumper harness connector, located at the back of the intake manifold, and the knock sensor connector. Refer to Circuit Testing in Wiring Systems.
3. If you find a condition, repair as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
—
Go to Step 10
Go to Step 7
7
Replace the appropriate Knock Sensor. Refer to Knock Sensor Replacement .
Is the action complete?
—
Go to Step 10
—
8
1. Inspect for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
2. If you find a poor connection repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.
Did you find and repair the condition?
—
Go to Step 10
Go to Step 9
9
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming .
Replace the PCM.
Is the action complete?
—
Go to Step 10
—
10
1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
2. Idle the engine at the normal operating temperature.
3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.
Does the scan tool indicate that this test ran and passed?
—
Go to Step 11
Go to Step 2
11
Select the Capture Info option and the Review Info option using the scan tool.
Does the scan tool display any DTCs that you have not diagnosed?
—
Go to the applicable DTC table
System OK
Circuit Description
The Knock Sensor (KS) system detects engine pre-detonation. The 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 (noise). 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 the engine produces. When the PCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set.
Conditions for Running the DTC
• The engine speed is between 1,650 RPM and 3,000 RPM.
• The MAP is more than 49 kPa.
• The engine coolant temperature is more than 60°C (135°F).
• The throttle angle is greater 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.
Action Taken When the DTC Sets
• The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
• The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
• The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
• A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
• Use a scan tool in order to clear the MIL and the DTC.
Diagnostic Aids
Important:
• Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
• For any test that requires probing the PCM or component harness connectors, use the J 35616 connector test adapter kit. Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems.
Inspect the knock sensor for proper installation. A knock sensor that is loose or over torqued may cause the DTC P0327 to set.
For an intermittent, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2 This verifies the malfunction is present. The scan tool will display DTC Ran=Yes and Pass=Int if the failure is intermittent. This indicates the diagnostic passed this ignition cycle and failed this ignition cycle. At this point the resistance of the knock sensors should be verified to be in the correct range. If the knock sensor resistances are correct, inspect the KS system wiring connections. When testing the KS system connections, start at the KS system jumper harness connector located behind the intake manifold. Then inspect the connections at the PCM. Refer to the wiring schematic for the correct connector and terminal. Then inspect the connections at the appropriate knock sensor. Failure Records data does not include the parameter KS Activity, however other parameters may aid in locating the conditions under which an intermittent occurred.
3 This test isolates the Knock Sensor from the rest of the circuit.
4 Tap on the engine block near the appropriate knock sensor. Do not tap on plastic engine components.
Step
Action
Value(s)
Yes
No
1
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?
—
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check
2
Important: If an engine knock can be heard, repair the engine mechanical condition before proceeding with this diagnostic. Refer to Engine Noise Diagnosis in Engine Mechanical.
1. Turn ON the ignition leaving the engine OFF.
2. Review the Freeze Frame and/or Failure Records data for this DTC and observe the parameters.
3. Turn OFF the ignition for 15 seconds.
4. Start the engine.
5. Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in Freeze Frame and/or Failure Records as possible. Special operating conditions that you need to meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running the DTC.
6. Monitor the Diagnostic Trouble Code (DTC) information using a scan tool.
Does the scan tool indicate that this diagnostic failed this ignition?
—
Go to Step 3
Go to Diagnostic Aids
3
1. Disconnect the knock sensor electrical connector located behind the intake manifold.
2. Measure the resistance between the appropriate knock sensor signal circuit (sensor side of harness) and the battery ground using the DMM.
3. Set the DMM to the 400K ohm scale.
Is the resistance of the knock sensor within the specified range?
93–107KΩ
Go to Step 4
Go to Step 6
4
1. Connect the DMM between the appropriate knock sensor signal circuit (sensor side of harness) and the engine block.
2. Set the DMM to the AC voltage scale.
3. Tap on the engine near the appropriate knock sensor while observing the signal indicated on the DMM.
Is any signal indicated on the DMM while tapping on the engine near the appropriate Knock Sensor?
—
Go to Step 5
Go to Step 7
5
1. Disconnect the PCM connector C1 located on the same side as the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
2. Test the KS signal circuit between the PCM and the knock sensor connector for the following:
• An open
• A short to voltage
• A short to ground
3. If you find a condition repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
—
Go to Step 10
Go to Step 8
6
1. Remove the intake manifold. Refer to Intake Manifold Replacement in Engine Mechanical–5.7L.
2. Test for an open or a short to ground in the signal circuit between the knock sensor jumper harness connector, located at the back of the intake manifold, and the knock sensor connector. Refer to Circuit Testing in Wiring Systems.
3. If you find a condition, repair as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
—
Go to Step 10
Go to Step 7
7
Replace the appropriate Knock Sensor. Refer to Knock Sensor Replacement .
Is the action complete?
—
Go to Step 10
—
8
1. Inspect for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
2. If you find a poor connection repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.
Did you find and repair the condition?
—
Go to Step 10
Go to Step 9
9
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming .
Replace the PCM.
Is the action complete?
—
Go to Step 10
—
10
1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
2. Idle the engine at the normal operating temperature.
3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.
Does the scan tool indicate that this test ran and passed?
—
Go to Step 11
Go to Step 2
11
Select the Capture Info option and the Review Info option using the scan tool.
Does the scan tool display any DTCs that you have not diagnosed?
—
Go to the applicable DTC table
System OK
10-08-2019, 12:13 PM
#9
Launching!
Thread Starter
Just to follow up on this issue, I replaced both knock sensors with what I believe to be genuine GM units. I torqued the sensors at 15 ft/pounds, built a dam of rtv around each one as described in the GM tsb ran the car through a couple drive cycles without the codes returning. As a side note, I measured the dc voltage on each sensor and read 35-37 millivolts at engine idle and 135-140 millivolts at 2000rpm. My meter is a Fluke88 and was set on a 400mv scale .Prior readings never exceeded 2-3 mv at idle or any other rpm. I really think that I got some foreign made fakes as I bought them online. We will see if the solution is a long term fix.