P1390 Mazda Code - Octane Adjust Out of Self-Test Range
Quick Answer
The Octane Adjust (OCT ADJ) shorting bar is used to retard spark timing. Common causes include Damage or missing Octane Adjust (OCT ADJ) cap. 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
- P1390 Mazda indicates Octane Adjust Out of Self-Test Range.
- Common causes
- Common causes include Damage or missing Octane Adjust (OCT ADJ) cap.
- 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 P1390 Mazda Description
The purpose of the OCT ADJ self-test is to check the state of the OCT ADJ shorting bar. A Diagnostic Trouble Code (DTC) will be present if the shorting bar is removed or if there is an open circuit. The OCT ADJ shorting bar is similar in shape to the SPOUT in-line connector. On some applications the Power Steering Pressure (PSP) circuit will also have a similar shorting bar connector. DO NOT remove the shorting bar unless directed by a Technical Service Bulletin (TSB).
If you don't have the bar, your timing has been retarded.
What are the Possible Causes of the DTC P1390 Mazda?
- Damage or missing Octane Adjust (OCT ADJ) cap
How to Fix the DTC P1390 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 P1390 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.
Need more information about the P1390 Mazda code?
Need more information on how to fix the P1390 Mazda code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P1390 Mazda code diagnosed by a professional: Find a repair shop in your area
Frequently Asked Questions about P1390 Mazda Code
1. What does the OBDII code P1390 mean on a Mazda?
P1390 on a Mazda indicates "Octane Adjust Out of Self-Test Range," meaning the engine's octane adjustment is outside the acceptable range detected by the ECU.
2. What are common symptoms of the P1390 code on a Mazda?
Symptoms may include reduced engine performance, poor fuel economy, possible engine knocking, and an illuminated check engine light.
3. What causes the P1390 code to be triggered?
Common causes include using fuel with an incorrect octane rating, a faulty knock sensor, incorrect timing adjustments, or an issue with the ECU.
4. Can using the wrong fuel cause the P1390 code?
Yes, using fuel with an octane rating lower than recommended can cause the octane adjustment to go out of range and trigger the P1390 code.
5. How can the P1390 code affect engine performance?
The code may result in reduced power, hesitation, or knocking as the engine struggles to adjust to improper fuel or timing.
6. How do you diagnose the P1390 code on a Mazda?
Diagnosis typically involves checking the fuel octane rating, inspecting the knock sensor, verifying timing settings, and scanning the ECU for related faults.
7. Is it safe to drive a Mazda with the P1390 code?
While it may be safe to drive short-term, prolonged driving with this code can lead to engine damage due to knocking or improper timing.
8. How can the P1390 code be fixed?
Fixes may include refueling with the correct octane-rated fuel, replacing a faulty knock sensor, or reprogramming the ECU if timing adjustments are needed.
9. Can a faulty knock sensor trigger the P1390 code?
Yes, a malfunctioning knock sensor can send incorrect signals to the ECU, resulting in the octane adjustment being out of range.
10. Will resetting the ECU clear the P1390 code in a Mazda?
Resetting the ECU may temporarily clear the code, but the underlying issue must be addressed to prevent the code from returning.
Discuss the causes and fixes for P1390 Mazda OBDII Code
Code P1390 Mazda comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
