DTC P1138 [YF (2.0L Zetec)]

id0102d0823400

DTC P1138

Lack of HO2S (Rear) switch, sensor indicates rich

DETECTION CONDITION

• The PCM monitors HO2S-12 signal switching during forced lean at PCM terminal 93. If the PCM does not detect signal input from HO2S-12 for calibrated amount of time, the PCM determines that HO2S-12 cannot switch to lean.

POSSIBLE CAUSE

• Pinched, shorted, and corroded wiring and pins
• Crossed sensor wires
• Exhaust leaks
• Contaminated or damaged HO2S-12

Diagnostic procedure

STEP

INSPECTION

ACTION

1
VERIFY FREEZE FRAME DATA HAS BEEN RECORDED
• Has 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 REPAIR INFORMATION AVAILABILITY
• Verify related service 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
INDETIFY TRIGGER DTC FOR FREEZE FRAME DATA
• Is DTC P1138 on FREEZE FRAME DATA?
Yes
Go to the next step.
No
Go to FREEZE FRAME DATA DTC inspection.
4
VISUALLY INSPECT FOR HO2S-12
Note
• Refer to the PCM connector pin number in the beginning of this pinpoint test.
• If necessary to address all Continuous Memory Ignition and Misfire DTCs, if received during Continuous Memory testing, before addressing any KOER HO2S-12
• Visually inspect for HO2S-12 followings:
- Pinched, shorted and corroded wiring and pins
- Crossed sensor wires
- Exhaust leakage
- Contaminated or damaged sensor
• Were any concerns found during inspection?
Yes
Repair or replace for malfunctioning part, then go to Step 12.
No
Go to the next step.
5
CHECK EXHAUST SYSTEM FOR LEAKS
• Place vehicle on a host, transaxle in P position, parking brake applied, raise vehicle.
• Inspect the following:
- Exhaust flanges for leaks
- HO2S-12 tightening torque
- Check for punctures and cracks in catalyst and pipes leading to them.
• Is an exhaust leak present?
Yes
Repair or replace malfunctioning part, then go to Step 12.
No
Go to the next step.
6
CHECK HO2S-12 HARNESS CIRCUIT FOR SHORT TO VPWR AND GROND
• Disconnect PCM and HO2S-12.
• Measure the resistance between following terminals at PCM harness side connector.
- Between terminal 35 and 90
- Between terminal 35 and 71, 97
• Is the resistance greater than 10,000 ohms?
Yes
Go to the next step.
No
Repair for short to ground circuit, then go to Step 12.
7
CHECK HO2S-12 SIGNAL CIRCUIT AND HO2S-12 SIGNAL RETURN CIRCUITS FOR OPEN IN HARNESS
• Measure resistance following at harness side connector.
- Between HO2S-12 terminal 1 and PCM terminal 71, 97
- Between HO2S-12 terminal 4 and PCM terminal 35
- Between HO2S-12 terminal 3 and PCM terminal 91
• Is the resistance less than 5.0 ohms?
Yes
Go to the next step.
No
Repair for open circuit, then go to Step 12.
8
CHECK HO2S-12 CIRCUIT VOLTAGE
• Connect PCM and HO2S-12.
• Connect the WDS or equivalent to DLC-2.
• Turn the ignition switch to ON.
• Access O2S11 PID.
• Is the voltage greater than 1.5 V?
Yes
Go to Step 11.
No
Go to the next step.
9
CHECK HO2S-12 GND CIRCUIT IN PCM
• Disconnect PCM.
• Measure the resistance between terminal 91 and 24, 51, 76, 103 at PCM connector.
• Is the resistance less than 5.0 ohms?
Yes
Go to the next step.
No
Replace PCM, then go to Step 12.
10
HO2S-12 CIRCUIT CHECK
• Connect PCM.
• HO2S-12 disconnected.
• Jumper terminal 1 and 4 at HO2S-12 harness side connector.
• Turn the ignition switch to ON.
• Access O2S12 PID.
• Is the O2S12 PID value greater than 1.5 V?
Yes
Replace HO2S-12, then go to Step 12.
No
Replace PCM, then go to Step 12.
11
CHECK FOR OVER VOLTAGE ON HO2S-12 CIRCUIT IN PCM
• Turn the ignition switch to ON.
• HO2S-12 disconnected.
• Measure voltage for following:
- Between terminal 3 at HO2S-12 harness side connector and battery negative post.
- Between terminal 4 at HO2S-12 harness side connector and battery negative post.
• Is the voltage greater than 1.5 V?
Yes
Replace PCM, then go to the next step.
No
Replace HO2S-12, then go to the next step.
12
VERIFY TROUBLESHOOTING OF DTC P1138 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Clear the DTC from the PCM memory using the WDS or equivalent.
• Perform KOER self test.
• Is the PENDING CODE same DTC present?
Yes
Replace PCM, then go to the next step.
No
Go to the next step.
13
VERIFY AFTER REPAIR PROCEDURE
• Perform "After Repair Procedure".
• Is there any DTC present?
Yes
Go to the applicable DTC inspection.
No
Troubleshooting completed.