Jeep Check Engine Light Stays On

Is the Check Engine Light appearing on your Jeep? Learn the cause of why the check engine light is illuminating and know the possible solutions for the warning light to turn off using an OBD-II Scanner.

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Jeep check engine light (CEL) comes on when the On-Board Diagnostic (OBD) system detects a problem with the engine, transmission, or evaporative system. This article covers common problems that trigger the Jeep check engine light to come on, symptoms, and how to read the fault codes yourself with an OBD-II scanner.

Symptoms

Common symptoms that you notice when Jeep check engine light comes on:

• Check engine light always on
• Engine runs rough
• Engine misfire present
• Lack of engine power
• Poor throttle response
• Engine noise
• Smoke from exhaust
• Overheating

What does the check engine light mean on a Jeep?

When your Jeep check engine light comes on, the onboard diagnostic system has detected a problem with the engine, emission system, and in some cases, even the transmission. The most common problems that trigger Jeep check engine lights to come on are worn spark plugs, bad oxygen sensors, or loose gas caps.

How to Reset Jeep Check Engine Light

The first step in the troubleshooting process is to read the fault codes from the Engine Control Unit. This is a simple procedure you can perform yourself with an OBD-II scanner.

1. Locate the OBD-II port under the dashboard and plug in your scanner.
2. Turn on the ignition but do not start the vehicle.
3. Please turn on the scanner and allow it to communicate with the vehicle.
4. Select Read Codes or Read Fault Codes, depending on the scanner.

Fix the problems that came up when you read the codes. Go back to the main menu and select Clear Fault Codes. If problems were not addressed, the check engine light would return.

Write down the codes that show on the screen of your OBD-II scanner. For example, a fault code may show as P0301 or P0300. Research those codes to get a better understanding of the problem.

What triggers the check engine light on a Jeep?

The most common causes that trigger check engine lights include:

• MAF Sensor
• Oxygen Sensor
• Spark Plugs
• Ignition Coils
• Catalytic Converter
• Loose Gas Cap

The next section covers a few other problems that trigger the Jeep check engine light.

• Thermostat: Engine thermostats stuck or not opening all the way are a fairly common problem on Jeep vehicles. Other than a check engine light, you might also experience engine overheating or high fuel consumption, depending on the failure mode. In both cases, the thermostat should be replaced without delay. Code: P0128 – thermostat not performing properly
• EGR Valve: On Jeep engines, EGR-related problem is usually caused by a stuck EGR valve. If stuck open, this can cause rough running, misfire, and stalling. In most cases, a carbon buildup within the valve prevents proper operation. If not too severe, this can be cleaned with EGR cleaner spray. Code: P0404 – EGR performance
• Catalytic Convert: Higher-mileage Jeeps are likely to have issues with emission control systems. In most cases, this is caused either by a worn catalytic converter or dirty O2 sensors. Pinpoint the root of the problem before replacing expensive parts. Codes: P0420 and P0430 – Catalyst Efficiency Below Threshold
• EVAP Leak: A check engine light with a strong gas odor could indicate a leak within the EVAP system.  Purge solenoid is the first thing to check for leaks and fuel ventilation lines. Some models have a Leak Detection Pump, which can go bad. Codes: P0456 – small evap leaks, P1494 – Leak Detection Pump faulty or evap leak.
• Transmission: Gearbox-related problems can trigger the check engine light, as well. You may be experiencing harsh shifting or being stuck in 2nd gear, called a  limp mode. In most cases, replacing the transmission valve body fixes the problem. Fault Code: P0740
• Throttle Body: Newer Jeeps with 4-cylinder engines are prone to electronic throttle body problems. This will cause rough idle, loss of power, and poor throttle response. In some cases, it can even trigger extremely limiting limp home mode. Replacing the throttle body is the only way to solve the issue. Codes: P2112 and P2112 – Throttle Actuator Control System – Stuck Open

Why does the Jeep check engine light flash on and off?

Be extra careful if the Jeep check engine light flashes, especially if accompanied by engine shaking and juddering.

This is a telltale sign of an engine misfire, causing damage to the catalytic converter and other engine components.

It is not recommended to drive a Jeep if the check engine light flashes.

Frequently Asked Questions

We hope you find the Jeep Check Engine Light Stays On guide helpful. Check these troubleshooting and repair guides for more help on your Jeep.