DTC P0720, P0721, P0722 [LA4AX-EL (CD4E)]

id0502a3806300

DTC P0720

Output shaft speed (OSS) sensor malfunction

DTC P0721

Output shaft speed (OSS) sensor signal noise

DTC P0722

Output shaft speed (OSS) sensor intermittent signal input

DETECTION CONDITION

• P0720: PCM detects that insufficient OSS sensor signal while driving
• P0721: PCM detects noise from OSS sensor signal while driving
• P0722: PCM detects intermittent OSS sensor signal input while driving

POSSIBLE CAUSE

• OSS sensor malfunction.
• Short to ground in wiring harness between OSS sensor terminal A (wiring harness-side) and PCM terminal 84 (wiring harness-side).
• Short to power supply in wiring harness between OSS sensor terminal A (wiring harness-side) and PCM terminal 58 (YF (2.0L Zetec) (2.0L Zetec))/84 (AJ (3.0L Duratec) (3.0L Duratec)) (wiring harness-side).
• Short to power supply in wiring harness between OSS sensor terminal B (wiring harness-side) and PCM terminal 23 (YF (2.0L Zetec) (2.0L Zetec))/3 (AJ (3.0L Duratec) (3.0L Duratec)) (wiring harness-side).
• Open circuit in wiring harness between OSS sensor terminal A (wiring harness-side) and PCM terminal 84 (wiring harness-side).
• Open circuit in wiring harness between OSS sensor terminal B (wiring harness-side) and body ground.
• Damaged connectors between OSS sensor and PCM.
• PCM malfunction.

Diagnostic procedure

STEP

INSPECTION

ACTION

1

VERIFY FREEZE FRAME DATA HAS BEEN RECORDED

• Has the FREEZE FRAME DATA been recorded?
Yes
Go to the next step.
No
Record the FREEZE FRAME DATA on the repair order, then go to the next step.
2

VERIFY RELATED REPAIR INFORMATION AVAILABILITY

• Verify related Service Bulletins and or/on-line repair information availability.
• Is any related repair information available?
Yes
Perform repair or diagnosis according to the available repair information.
• If the vehicle is not repaired, go to the next step.
No
Go to the next step.
3
INSPECT OSS SENSOR CONNECTOR FOR POOR CONNECTION
• Turn the ignition switch to the LOCK position.
• Disconnect the OSS sensor connector.
• Inspect for poor connection (such as damaged/pulled-out pins, corrosion)
• Is the connection normal?
Yes
Go to the next step.
No
Repair or replace connector and/or terminal, then go to Step 9.
4

INSPECT OSS SENSOR CIRCUIT FOR SHORT TO GROUND

• Inspect for continuity between OSS sensor connector A (wiring harness-side) and body ground.
• Is there continuity?
Yes
Repair or replace the wiring harness, then go to Step 9.
No
Go to the next step.
5

INSPECT PCM CONNECTOR FOR POOR CONNECTION

• Disconnect the PCM connector.
• Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
• Is the connection normal?
Yes
Go to the next step.
No
Repair or replace the connector and/or terminals, then go to Step 9.
6

INSPECT OSS SENSOR CIRCUIT FOR OPEN CIRCUIT

• Inspect the following OSS sensor terminals (wiring harness-side) and PCM terminals (wiring harness-side):
YF (2.0L Zetec) (2.0L Zetec)
- A and 58
- B and 23
AJ (3.0L Duratec) (3.0L Duratec)
- A and 84
- B and 3
• Is there continuity?
Yes
Go to the next step.
No
Repair or replace the wiring harness, then go to Step 9.
7

INSPECT OSS SENSOR CIRCUIT FOR SHORT TO POWER SUPPLY

• Turn the ignition switch to the ON position (engine off).
• Inspect the voltage at OSS sensor terminals A and B (wiring harness-side).
• Is the voltage 0 V?
Yes
Go to the next step.
No
Repair or replace the wiring harness, then go to Step 9.
8

INSPECT OSS SENSOR

• Inspect the OSS sensor.
• Is OSS sensor normal?
Yes
Go to the next step.
No
Replace the OSS sensor, then go to the next step.
9
VERIFY TROUBLESHOOTING OF DTC P0720 P0721 OR P0722 COMPLETED
• Make sure to reconnect all the disconnected connectors.
• Clear the DTC from memory using the WDS or equivalent.
• Perform the "After Repair Procedure".
• Are any DTCs present?
Yes
Replace the PCM, then go to the next step.
No
Go to the next step.
10
VERIFY DTCS
• Are except DTC P0720, P0721 and P0722 output?
Yes
Go to the applicable DTC inspection.
No
DTC troubleshooting completed.