Engine-Codes - Jeep - P0138 Jeep

P0138 Jeep Code - O2 Sensor 1/2 Circuit High

- Code Popularity: 76,230 Views
- Repair Importance Level: 2/3
- Repair Difficulty Level: 2/3
Table of contents
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What are the Possible Causes of the DTC P0138 Jeep?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Faulty Rear Heated Oxygen Sensor Bank 1
  • Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
  • Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
  • Intake air leaks
  • Exhaust gas leaks
  • Inappropriate fuel pressure
  • Faulty fuel injectors

Code Tech Notes

Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.





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How to Fix the DTC P0138 Jeep?

Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

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What is the Cost to Diagnose the Code?

Labor: 1.0

The cost to diagnose the P0138 Jeep code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.

When is the Code Detected?

The P0138 code is set when the Engine Control Module (ECM) detects that the rear O2 sensor signal voltage remains excessively high for an extended period of time.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)
  • High Fuel Consumption
  • Excessive Smoke from Exhaust

What Does the P0138 Jeep Code Mean?

The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.

P0138 Jeep Code - O2 Sensor 1/2 Circuit High

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