Diagnostic Aids

Perform this test when directed by QUICK TEST . This CIRCUIT TEST is intended to diagnose:

• PTO wiring harness circuit.
• Powertrain Control Module (PCM).

Fig 1: PT0 Test Circuit & Switch Schematic

1. Step 1) Check PTO Switch For Short To Power  PTO signals PCM that additional load is being applied to engine. If PTO circuit failure occurs, a fault code may be set. Possible causes for this code are:
   • PTO circuit shorted to power.
   • Faulty Powertrain Control Module (PCM).

   Turn ignition off. Disconnect PTO switch wiring harness connector. Connect scan tester to DLC. Turn ignition on. Access PTO STAT PID. If PTO STAT PID is on, go to next step. If PTO STAT PID is off, repair or replace switch as necessary. Road test vehicle and repeat QUICK TEST .

2. Step 2) Check PTO Circuit For Short To Power  Leave ignition off and PTO switch disconnected. Disconnect PCM 104-pin connector. Inspect connector for damage and repair as necessary. Measure voltage test pin No. 4 and test pins No. 51 and 103 at breakout box. If voltage is less than one volt, replace PCM and repeat QUICK TEST . If voltage is one volt or more, repair circuit short to power and repeat QUICK TEST .
3. Step 3) MIL On: Check PTO PID  Turn ignition off. Connect scan tester to DLC. Turn ignition on. Access PTO STAT PID. If PTO STAT PID is available and displaying on or off, go to next step. If PTO STAT PID is not as specified, go to step 9).
4. Step 4) Check PTO Circuit With Scan Tester  With ignition on and PTO STAT PID accessed, cycle PTO switch. If PTO STAT PID cycles on, delays, and then cycles off, PTO input is okay and testing is complete. If PTO STAT PID does not cycle as specified, go to next step.
5. Step 5) Check PTO Circuit For Short To Ground  Turn ignition off. Leave PTO switch disconnected. Disconnect scan tester from DLC. Measure resistance between chassis ground and PTO circuit terminal at PTO switch connector. If resistance is 10,000 ohms or less, go to next step. If resistance is more than 10,000 ohms, go to step 7).
6. Step 6) Isolate Short To Chassis Ground  Leave ignition off and PTO sensor disconnected. Disconnect PCM 104-pin connector. Inspect connector for damage and repair as necessary. Install EEC-V Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 4 (PTO) and test pins No. 77 and 103 at breakout box. If resistance is more than 10,000 ohms, replace PCM and repeat QUICK TEST . If resistance 10,000 ohms or less, repair PTO circuit short to chassis ground, repeat QUICK TEST .
7. Step 7) Leave ignition off and PTO sensor disconnected. Connect scan tester to DLC. Connect jumper wire between positive battery terminal and PTO terminal at PTO switch wiring harness connector. Turn ignition on. Access PTO STAT PID. If PTO STAT PID is on, PTO input is okay and testing is complete. Check switch for malfunction and repair as necessary. If PTO STAT PID is off, go to next step.
8. Step 8) Check Circuit Continuity  Leave ignition off and PTO sensor disconnected. Disconnect PCM 104-pin connector. Inspect connector for damage and repair as necessary. Install EEC-V Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 4 (PTO) and PTO circuit terminal at PTO switch connector. If resistance is less than 5 ohms, replace PCM and repeat QUICK TEST . If resistance is 5 ohms or more, repair open in PTO circuit and repeat QUICK TEST .
9. Step 9) Perform KOEO and KOER self-test. If any DTCs are present, repair as necessary. If no DTCs are present, go to next step.
10. Step 10) Road test vehicle under various conditions. Retrieve all Continuous Memory DTCs and service as necessary. If no DTCs are present, fault cannot be duplicated at this time. If symptom is still present, go to CIRCUIT TEST Z.