Jeep Check Engine Light Stays On

Is the Check Engine Light on in your Jeep? This guide will help you troubleshoot and come up with possible solutions using an OBD-II Scanner. Are you more of a visual learner? Follow along with our video guide!

The 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 will cover common problems that trigger is warning light to come on, symptoms, and how to read the fault codes yourself with an OBD-II scanner.

Symptoms

Some symptoms that you might notice when your Jeep’s check engine light comes on:

• The check engine light is always on.
• The engine runs rough.
• An engine misfire is present.
• Lack of engine power.
• Poor throttle response.
• Engine noise.
• Smoke from exhaust.
• Overheating.

What does this warning light mean on a Jeep?

When your Jeep’s CEL 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 the warning to come on are worn spark plugs, bad oxygen sensors, or loose gas caps.

How to Reset a Jeep CEL

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. Turn on the scanner and allow it to communicate with the vehicle.
4. Select ‘Read Codes’ or ‘Read Fault Codes’, depending on the scanner.

After a sucessful scan, your scanner will present a list of diagnostic trouble codes (DTC). In order to make your CEL clear properly, you have to fix the problems presented by the “present” or “active” codes first. Once these issues have been resolved, return to the main menu and select ‘Clear Fault Codes’. If problems are not addressed, the warning light and DTCs will return.

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

What triggers the check engine light on a Jeep?

The most common causes that will trigger the CEL include a faulty:

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

The next section covers a few other problems that can trigger the Jeep’s CEL:

• 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 CEL with a strong gas odor could indicate a leak within the EVAP system.  The 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 an 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.

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.

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