AutoCodes – Generic – P1399

P1399 Code - Random Cylinder Misfire Detected

Quick Answer

When a misfire occurs, engine speed will fluctuate. Common causes include Valve clearance out of range, Blocked EGR (exhaust gas recirculation) Passages. 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: P1399 indicates Random Cylinder Misfire Detected.
Common causes: Common causes include Valve clearance out of range, Blocked EGR (exhaust gas recirculation) Passages.
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.

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Code Popularity 18,497

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 29, 2022

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes ▶
Cost to Diagnose
FAQs
Comments
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Code P1399 Description

When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring, and the Diagnostic Trouble Code (DTC) will be set.

OBDII Code P1399 - Random Cylinder Misfire Detected - AutoCodes.com — P1399 Code - Random Cylinder Misfire Detected

What does this mean?

What are the Possible Causes of the DTC P1399?

Valve clearance out of range
Blocked EGR (exhaust gas recirculation) Passages

How to Fix the DTC P1399?

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 does this mean?

Code Tech Notes

Adjusting the valves will usually fix this problem.

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1399 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 P1399 code?

Need more information on how to fix the P1399 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1399 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P1399 Acura — Random Cylinder Misfire Detected
P1399 Audi — Engine RPM Signal TD Short To B+
P1399 Buick — Wheel Speed Sensor 2 G-Sensor Circuit Intermittent
P1399 Cadillac — Wheel Speed Sensor 2 G-Sensor Circuit Intermittent
P1399 Chevrolet — Wheel Speed Sensor 2 G-Sensor Circuit Intermittent
P1399 Chrysler — Wait To Start Lamp Circuit Condition
P1399 Dodge — Wait To Start Lamp Circuit Condition
P1399 Ford — Glow Plug Circuit High Side High Input
P1399 GMC — Wheel Speed Sensor 2 G-Sensor Circuit Intermittent
P1399 Honda — Random Cylinder Misfire Detected
P1399 Volkswagen — Engine RPM Signal TD Short To B+

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P1399 Code

1. What are the common symptoms of OBDII code P1399 (Random Cylinder Misfire Detected)?

- Common symptoms include rough idling, engine hesitation, loss of power, and potential stalling.

2. What are the possible causes of OBDII code P1399?

- The causes can include issues with spark plugs, ignition coils, fuel injectors, vacuum leaks, or even a faulty engine control module (ECM).

3. How can I diagnose the source of the random cylinder misfire indicated by code P1399?

- Diagnosing the issue may involve conducting a thorough inspection of spark plugs, ignition coils, fuel injectors, and checking for any vacuum leaks.

4. Can a dirty or clogged fuel injector cause OBDII code P1399?

- Yes, a dirty or clogged fuel injector can disrupt the fuel-air mixture ratio and lead to random cylinder misfires triggering code P1399.

5. Are there any DIY repair tips for addressing OBDII code P1399?

- DIY repair tips may include checking and replacing faulty spark plugs, ignition coils, or cleaning fuel injectors. However, for more complex issues, professional help may be needed.

6. Will driving with OBDII code P1399 damage my vehicle further?

- Continuing to drive with code P1399 may cause damage to the catalytic converter and other engine components over time, so it's best to address the issue promptly.

7. Can a simple reset of the OBDII system clear code P1399?

- While resetting the system may temporarily clear the code, it will likely return if the underlying issue causing the misfire is not addressed.

8. Is it safe to ignore OBDII code P1399 if my vehicle seems to be running fine?

- Ignoring code P1399, even if the vehicle appears to be running fine, can lead to decreased fuel efficiency, increased emissions, and potential long-term engine damage.

9. How important is it to address OBDII code P1399 promptly?

- Promptly addressing code P1399 is crucial to prevent further damage to the engine, ensure optimal performance, and maintain fuel efficiency.

10. Can extreme weather conditions contribute to triggering OBDII code P1399?

- Yes, extreme weather conditions such as extreme cold or heat can impact the engine's performance and potentially contribute to triggering code P1399.