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by Bob O’Neill and Bob Lincoln
These pages helps to describe the fault codes for the Chrysler electronic fuel injection engine control units (ECU) for 2.2L and 2.5L engines (and, in many cases, V6 engines) from 1984 through 1994. You don’t need any special computer scanners to read these codes; all you need is your ignition key.
Before we begin the process of learning what if any codes have been set in the computer, it is a good idea to understand the components involved. The primary brain of the system is the Engine Control Unit or ECU, sometimes called the logic module. The ECU is a computer with a processor, memory, and some read-only memory which holds fuel tables and other values used to make decisions about drivability and performance. It also contains the voltage regulator circuit after 1985; power circuits for ignition, fuel injection, and relay drivers.
In later years, a Power Control Module is also used (it’s next to the battery), and a logic module can be found behind the passenger kickpad. It receives the engine sensor information, decides how to react, and passes signals to the PCM to adjust engine operation. In later years (1990s and up), the Power Control Module and logic module were combined into one computer, called either a SMEC or SBEC, and stored in the engine bay, usually near the battery; a Body Control Module inside the car, behind the kickpad, controls functions such as lights, power locks, and timers.
It is important to understand the different sensors. There are pages which detail each of these but here is a brief definition. Click on the name of the sensor to read a more detailed explanation.
Also see newer fault codes (1990s-onwards)
The first step in troubleshooting drivability issues is to pull your fault codes.
Be sure the engine is not running. Then do the ‘Key Dance’. This means that within 5 seconds:
turn the key to ‘ON’ (not start) and then ‘OFF’ repeatedly, in this order: ON-OFF-ON-OFF-ON.
Be sure to leave the key in the ‘ON’ position and watch the red ‘Power Limited’, ‘Check Engine’ or ‘Limited’ light (we’ll refer to this as the ‘Power Limited’ light). One of the first diagnostic steps is to see if the light comes on at all. If it does not then you probably have a burned out bulb; replace it and start with the ‘Key Dance’ again. (If you’re a real beginner — you will find the bulb specifications in the owner’s manual.)
Looking at the Power Limited light, count the flashes. These will come in sets of two flashes. For example if you count one flash then after a pause two more that’s a code 12. This will be followed by five flashes and a pause then five more. This is a code 55 or ‘end of file’. Codes will always end in a code 55 and there will be no more flashes. This is the computer’s way of telling you that it’s all done. If the only code you receive is a 55 then you ‘have no fault codes’ and the computer has nothing to report.
Sometimes it takes a while to get used to reading the flashes, but remember that the delays are important, so watch for them — but not too hard (there are no three-digit codes!) There are also no numbers higher than 7— you'll never see more than seven flashes in a row.
Usually fault codes will remain in the memory of the ECU for about 15 engine starts. If you want to clear these codes after you've repaired the system, you can do so by disconnecting the battery for a short time (which will also wipe out your radio stations; if you have a four-speed automatic, it should be retrained). The codes will usually clear in a few minutes but it may take as much as 10 minutes without battery power.
If you check the codes again after disconnecting the battery, you'll see a code 11, 12 and 55. Codes 11 will be removed from the report the next time the engine starts, and code 12 (“battery disconnected”) after about 15 starts. Code 55 will always be reported because it’s the “end of file” indicator — it’s always there to show that you did what was needed to get a “code dump.”
When a major sensor fails, the computer will enter “limp mode.” In limp mode the computer doesn’t listen to the information from the failed sensor and relies on internal tables for things like timing and fuel delivery.
Limp mode is just what it sounds like. It allows you to ‘limp’ into the dealer or repair center to have the problem repaired. Limp mode may cause the engine to run poorly and the power limited light will be lit; four-speed automatic transmissions may be limited to second or third gear. If the power limited light comes on, check your codes to help you pinpoint where the problem is.
There is one thing to consider when troubleshooting drivability issues. Even if the computer throws a fault code it doesn’t mean that the sensor is at fault. Please read ‘How to troubleshoot drivability issues’ before replacing any parts.
Once you have taken the steps outlined in the ‘How to troubleshoot driveability issues’ and have cleared the codes by disconnecting your battery for a few minutes, if your ECU reports a code, check the links below. Each of these pages outlines the reason for the code and some information about the sensor in question. They also give information about how to further troubleshoot to see if it is indeed the sensor reported by the associated code.
Newer fault codes (1990s-onwards)
Sensors, Switches, and Other Systems | Main Repairs Page | EEKs
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