Diagnostic Aids

Perform this test only when directed by QUICK TEST . This test is intended to diagnose the following:

• Knock Sensor (KS).
• Wiring harness circuits (KS and SIG RTN).
• Powertrain Control Module (PCM).

To prevent replacement of good components, be aware the following non-EEC related areas may be at fault:

• Poor fuel quality.
• Ignition system.
• Ignition or valve timing.
• Engine mechanical condition.

Fig 1: Single KS Sensor Test Circuits & Connector Terminals

Fig 2: Dual KS Sensor Test Circuits & Connector Terminals

1. Step 1) Check Sensor Voltage  DTC P0325, P0326, P0330 and P0331 indicate that ignition timing was not adjusted after spark knock has occurred. Possible causes for this fault are:
   • High altitude interference.
   • Open or short in harness.
   • Faulty knock sensor.
   • Faulty Powertrain Control Module (PCM).

   Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for damaged and repair as necessary. Install EEC-V Breakout Box (014-00950). Connect PCM to breakout box. Turn ignition on. Measure voltage between suspect sensor test pin and test pin No. 91 (SIG RTN). If voltage is 2.4-2.6 volts, go to next step. If voltage is less than 2.4 volts, go to step 5). If voltage is more than 2.6 volts, go to step 6).

2. Step 2) Check For Intermittent Circuit Fault  Leave ignition on. Measure voltage between suspect sensor test pin and test pin No. 91. While observing voltmeter, wiggle small sections of wiring harness starting at the knock sensor and going to the PCM. Lightly tap on knock sensor and PCM. If voltmeter reading stays within normal operating range (2.4-2.6 volts), go to next step. If voltmeter reading goes out of range, isolate fault and repair as necessary. Clear PCM memory and repeat QUICK TEST .
3. Step 3) Check For Voltage Increase  Turn ignition off. Leave PCM connected to breakout box. Disconnect scan tester from DLC. Set voltmeter on AC scale. Start engine and allow to idle. Measure voltage between suspect sensor test pin and test pin No. 91. Raise engine speed to 3000 RPM. If AC voltage increases, replace PCM and repeat QUICK TEST . If AC voltage does not increase, go to next step.
4. Step 4) Check Circuit Continuity  Turn ignition off. Disconnect PCM from breakout box. Disconnect suspect sensor. Measure resistance of KS circuit (KS1 or KS2) between suspect sensor connector terminal and breakout box. Measure resistance of SIG RTN circuit between suspect sensor connector terminal and breakout box. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST .
5. Step 5) Check Circuit For Short To Ground  Leave suspect sensor disconnected. Measure resistance between KS circuit (KS1 and KS2) test pins and test pin No. 91. Measure resistance between KS circuit test pins and the following power ground test pins No. 24, 51, 76, 77 and 103. Measure resistance between KS circuits and ground. If all resistance measurements are 10,000 ohms or more, replace knock sensor and repeat QUICK TEST . If any resistance measurement is less than 10,000 ohms, repair short circuit and repeat QUICK TEST .
6. Step 6) Check Circuit For Short To Power  Leave ignition on. Measure voltage between KS circuit (KS1 and KS2) test pins and the following power ground test pins No. 24, 51, 76, 77 and 103. If each voltage measurement is less than 0.5 volt, replace PCM and repeat QUICK TEST . If any voltage measurement is 0.5 volt or more, repair circuit short to power and repeat QUICK TEST .