Diagnostic Aids

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

• Knock Sensor (KS).
• Harness circuit: KS.
• 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 timing.
• Engine mechanical condition.

1. DTC P0325
   
   DTC P0325 indicates that spark knock has occurred and knock sensor failed to detect. Possible causes for this fault are as follows:
   • PCM not receiving signal.
   • Open or short in harness.
   • Faulty knock sensor.
   • Faulty Powertrain Control Module (PCM).

   Turn ignition off. Disconnect PCM. Disconnect knock sensor in-line connector. Measure resistance of KS signal circuit (White wire) between PCM connector terminal No. 63 and KS in-line connector. Also measure resistance of GND circuit (Black/Red wire) between PCM harness connector terminal No. 45 and KS in-line connector. If resistances are less than 5 ohms, go to next step. If resistances are greater than 5 ohms, repair open circuit in White or Black/Red wires. See Fig 1. Also see CIRCUIT PIN IDENTIFICATION  table.

2. Check KS Circuit For Short To Ground
   
   Disconnect PCM. Disconnect KS in-line connector. Measure resistance of KS circuit between PCM connector terminal No. 63 (White wire) and GND terminal No. 45 (Black/Red wire). If resistance is greater than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, repair short circuit in wiring.
   Fig 1: Identifying KS Sensor Connector Terminals

   Courtesy of FORD MOTOR CO.
3. Check KS Circuits For Short To Power
   
   Disconnect PCM. Disconnect KS in-line connector. Measure resistance of KS circuit between PCM connector terminal No. 63 (White wire) and VPWR terminals No. 66 and 97 (Black/White wires). Also measure resistance between PCM connector terminal No. 63 (White wire) and KAPWR terminal No. 80 (Yellow wire). If each resistance measurement is greater than 10 k/ohms, go to next step. If each resistance measurement is less than 10 k/ohms, repair short circuit in wiring.
4. Check Resistance Of KS
   
   Ensure KS in-line connector is disconnected. Measure resistance between KS connector terminal White wire and ground. If resistance is 500-620 k/ohms, replace PCM. If resistance is not 500-620 k/ohms, replace knock sensor.