GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1996 🢒 DeVille 🢒 DTC 🢒 DTC P0327 Knock Sensor Circuit Low Voltage

Object Number: 13043 Size: SF
Engine Controls Components
Ignition Control (IC) Module
OBD II Symbol Description Notice
ESD Notice

Circuit Description

During engine operation, the knock sensor will detect background noise on its circuit. The PCM monitors this noise and compares the amount of noise it monitors to the amount it expects too see. If the knock sensor system is operating correctly the background noise will generally increase as engine speed and load increase. This background noise is used to detect knock sensor circuit faults. This DTC will set if the knock sensor background noise is below an expected learned value at a given RPM and TP sensor range for a given period of time.

Conditions for Setting the DTC

Test Conditions

    •  Ignition voltage at least 10 volts.
    •  Coolant Temperature at least 40°C (104°F).
    •  Throttle position at least 4.8 degrees.
    •  Engine speed at least 3000 RPM..
    •  Battery voltage at least 11 volts.

Failure Condition

The knock sensor background noise voltage is less than 0.5 volts above the learned minimum for 1 second.

Action Taken When the DTC Sets

    •  The PCM will illuminate the Malfunction Indicator Lamp (MIL) after two consecutive drive trips that the diagnostic runs and fails.
    •  The PCM will record operating conditions at the time the DTC sets. This information will be stored in the Freeze Frame and Failure Records.
    •  A first failure of this DTC will store in Last Test Failed but not History.

Conditions for Clearing the MIL/DTC

    •  The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
    •  A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
    •  A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test.
    • Use a scan tool to clear DTCs.
    • Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

Diagnostic Aids

Check for an intermittent open or short on CKT 496.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

  1. Checking knock sensor and knock sensor signal circuit under intake manifold.

    2.

  2. Checking if circuit or sensor is at fault.

    3.

  3. Checking knock sensor signal circuit to PCM.

    4.

  4. Checking if PCM is faulty or fault is not present.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to A Powertrain On Board Diagnostic (OBD) System Check

2

  1. Disconnect the knock sensor / starter solenoid harness connector, located on right side of engine compartment at rear corner of intake.
  2. Using DMM J 39200 set to AC volts 400 mV setting, measure frequency in Hertz at knock sensor connector terminal B (sensor side).
  3. Tap on block with non-metallic object.

Does frequency fluctuate while tapping on block?

--

Go to Step 5

Go to Step 3

3

  1. Remove intake manifold.
  2. Disconnect knock sensor connector at sensor.
  3. Measure the frequency in Hertz directly at the knock sensor.
  4. Tap on block with non metallic object.

Does frequency fluctuate while tapping on block?

--

Go to Step 4

Go to Step 9

4

Repair open or short to ground in knock sensor signal circuit between knock sensor and knock sensor / starter solenoid connector.

Is the repair complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--

5

  1. Reconnect knock sensor / starter solenoid connector.
  2. Using the scan tool, save the Freeze Frame and Failure Records data stored when the DTC set.
  3. Record the fluid life indexes, turn the key to OFF and wait 30 seconds.
  4. Disconnect PCM connector C2.
  5. Measure the frequency in Hertz at PCM connector C2 terminal 62.
  6. Tap on block with non-metallic object.

Does frequency fluctuate while tapping on block?

--

Go to Step 7

Go to Step 6

6

Repair open or short to ground in knock sensor signal circuit between PCM connector C2 and knock sensor / starter solenoid connector terminal B.

Is the repair complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--

7
  1. Reconnect PCM connector C2.
  2. Using Failure Rec. check the conditions under which the DTC set.
  3. Operate the vehicle under conditions noted.
  4. Ensure that all test conditions are met and the DTC runs.

Did the DTC reset?

--

Go to Step 8

Fault not present. Refer to Diagnostic Aids

8
  1. Check terminal contact at PCM connector C2 terminal 62.
  2. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 11

9
  1. Check terminal contact at the knock sensor.
  2. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 10

10

Replace the knock sensor. Refer to Knock Sensor (KS) Replacement .

Is the replacement complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--

11

Replace the PCM. Refer to PCM Replacement/Programming .

Is the replacement complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--