P1138 Mazda Code - Rear O2 Sensor Self Test Fault
Quick Answer
P1138 Mazda indicates Rear O2 Sensor Self Test Fault. Common causes include Faulty Rear O2 Sensor, Rear O2 Sensor harness is open or shorted, Rear O2 Sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P1138 Mazda indicates Rear O2 Sensor Self Test Fault.
- Common causes
- Common causes include Faulty Rear O2 Sensor, Rear O2 Sensor harness is open or shorted, Rear O2 Sensor circuit poor electrical connection.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code P1138 Mazda Description
What are the Possible Causes of the DTC P1138 Mazda?
- Faulty Rear O2 Sensor
- Rear O2 Sensor harness is open or shorted
- Rear O2 Sensor circuit poor electrical connection
How to Fix the DTC P1138 Mazda?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P1138 Mazda code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Frequently Asked Questions about P1138 Mazda Code
1. What does the OBDII code P1138 mean on a Mazda?
The P1138 code indicates a "Rear O2 Sensor Self Test Fault," meaning the oxygen sensor downstream of the catalytic converter failed its self-diagnostic test.
2. What are the common symptoms of code P1138 in a Mazda?
Symptoms may include an illuminated check engine light, poor fuel economy, rough idling, or failed emissions tests.
3. What causes the P1138 code in a Mazda?
Common causes include a faulty rear oxygen sensor, damaged wiring or connectors, exhaust leaks, or issues with the engine control module (ECM).
4. Can a dirty or clogged catalytic converter trigger the P1138 code?
Yes, if the catalytic converter is not functioning properly, it can affect the rear O2 sensor's readings and cause this code.
5. How do I fix the P1138 code on my Mazda?
Start by inspecting and replacing the rear oxygen sensor if necessary. Check for wiring damage, exhaust leaks, and ensure the catalytic converter is functioning correctly.
6. Is it safe to drive a Mazda with the P1138 code?
While it may be safe for short distances, driving with this code can lead to reduced fuel efficiency and potential damage to the catalytic converter over time.
7. Can a software update resolve the P1138 code in some Mazdas?
In rare cases, an ECM software update from the dealership may fix the issue if it’s related to a programming error.
8. How can I diagnose the P1138 code on a Mazda?
Use an OBDII scanner to confirm the code, inspect the rear O2 sensor and wiring, and check for exhaust system leaks.
9. What tools are needed to repair a P1138 code?
You’ll typically need an OBDII scanner, a multimeter for testing wiring, and basic tools to replace the oxygen sensor if required.
10. How much does it cost to fix the P1138 code on a Mazda?
Repair costs vary but replacing a rear O2 sensor typically ranges from $150 to $300, including parts and labor.
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