Engine-Codes - Infiniti - P0138 2004 INFINITI G35

P0138 2004 INFINITI G35 Code - HO2S12 Circuit High Voltage

- Code Popularity: 3,164 Views
- Repair Importance Level: 2/3
- Repair Difficulty Level: 2/3
Table of contents

|What are the Possible Causes of the P0138 2004 INFINITI G35 Code?

  • 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

|How to Fix the P0138 2004 INFINITI G35 Code?

Start by checking 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's pins.

|P0138 2004 INFINITI G35 code tech notes

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

|What is the cost to diagnose the P0138 2004 INFINITI G35 code?

Labor: 1.0

The cost to diagnose the P0138 2004 INFINITI G35 code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.

|When is the P0138 2004 INFINITI G35 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 P0138 2004 INFINITI G35 code possible symptoms?

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

|What Does the P0138 2004 INFINITI G35 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.

HO2S12 Circuit High Voltage

|Need more information with the P0138 2004 INFINITI G35 code?

Need more information on how to fix the P0138 2004 INFINITI G35 code?
Get Access to Factory Service Manuals

|Need help with a P0138 2004 INFINITI G35 code?

Get the P0138 2004 Infiniti G35 code diagnosed by a professional: Find a repair shop in your area