On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

FB: Power Take Off (PTO)

FB: Introduction

FB1 PTO PID DOES NOT CYCLE: CHECK FOR DEFECTIVE PTO SWITCH

Note: Causes of concern:

PTO circuit short to power in aftermarket switch/input to the PTO harness connector.
PTO circuit short to VPWR.
Damaged PCM.

Disconnect PTO switch harness connector.
Measure resistance across PTO switch while in on then off position.

Is resistance less than 5.0 ohms then greater than 10,000 ohms when cycling switch?

Yes	No
GO to FB2 .	REPAIR or REPLACE PTO switch. REFER to aftermarket component manufacturer for service information. RECONNECT PTO switch harness connector. PERFORM OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).

FB2 CHECK PTO CIRCUIT FOR SHORT TO VPWR

Disconnect PCM.
Key on, engine off.
Measure voltage of PTO circuit between PCM harness connector pin 4 and battery negative post.

Is voltage less than 1.0 volt?

Yes	No
RECONNECT PCM and PTO switch harness connector. GO to FB4 .	REPAIR short circuit.

FB3 MIL ON: CHECK PTO PID

Note: Causes of concern:

Open in PTO circuit.
Short to chassis ground in PTO circuit.

Connect scan tool to DLC.
Key on, engine off.
Access the PTO PID.

Is the PTO PID available and displaying on or off?

Yes	No
GO to FB1 .	GO to FB9 .

FB4 CHECK PTO CIRCUIT WITH SCAN TOOL

Note: This step requires operating the PTO component. Refer to aftermarket manufacturer for PTO operating instructions. Follow all safety precautions.

Key on (may need to start engine to engage PTO).
Cycle PTO switch/handle while viewing PTO PID.

Does PTO PID cycle ON, delay, then turn OFF?

Yes	No
RETURN to Section 3 , Symptom Charts.	KEY OFF. GO to FB5 .

FB5 CHECK PTO CIRCUIT FOR SHORT TO GROUND IN HARNESS

Disconnect PCM.
Disconnect scan tool from DLC.
Disconnect PTO switch harness connector.
Measure resistance of PTO circuit between PCM harness connector pin 4 and battery negative post.

Is resistance greater than 10,000 ohms?

Yes	No
RECONNECT PCM. GO to FB7 .	REPAIR short circuit.

FB7 CHECK PTO CIRCUIT FROM PTO SWITCH HARNESS CONNECTOR TO PCM

Connect scan tool.
Connect Jumper wire between B+ and PTO circuit at the PTO switch harness connector.
Key on, engine off.
Access PTO PID.

Is PTO PID on with jumper inserted and off with jumper removed?

Yes	No
RETURN to Section 3 , Symptom Charts.	KEY OFF. GO to FB8 .

FB8 CHECK PTO CIRCUIT RESISTANCE

Disconnect PCM.
Measure resistance of PTO circuit between PCM harness connector pin 4 and PTO switch harness connector.

Is resistance less than 5.0 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPAIR open PTO circuit.

FB9 PERFORM KOEO AND KOER QUICK TESTS

The following steps are used for PTO diagnostics when the vehicle does not support the PTO circuit or PID.

Perform KOEO and KOER Quick Tests. Refer to Section 3, Symptom Charts, Quick Test , QT1.

Are any KOEO or KOER DTCs present?

Yes	No
FOLLOW direction in Quick Test , QT1 to REPAIR the KOEO or KOER DTCs.	GO to FB10 .

FB10 PERFORM OBD II DRIVE CYCLE WITH PTO DISENGAGED

Note: This test step will determine if the PTO operation resulted in any Continuous Memory DTCs stored due to the extra load of the PTO component on the engine.

Perform PCM Reset.

Note: Make sure the PTO is disengaged.

Perform OBD II Drive Cycle (refer to Section 2 , Drive Cycles).
Retrieve all Continuous Memory DTCs (refer to Section 2 , Accessing All Continuous Memory DTCs).

Are any Continuous Memory DTCs stored?

Yes	No
GO to Section 4 , Powertrain Diagnostic Trouble Code (DTC) Chart, to ADDRESS the first Continuous Memory DTC.	MIL can be caused by engaging the PTO, creating a load on the engine, while the OBD II Monitors were running. If the symptom persists, GO to Pinpoint Test Step Z1 .