Note: Allpar does not take responsibility for the veracity of any information or opinion presented, does not claim expertise, has not necessarily verified or performed the fix, repair, or modification in this page, and is not responsible for any consequences. Please proceed at your own risk.
Chrysler, Plymouth, and Dodge Computer Codes
Chrysler Corporation (including Dodge and Plymouth) vehicles with fuel injection, like all current computer-controlled vehicles, watch their own behavior and set "error codes" when they see something which is not as it should be. Computers only do what you tell them, so they might not see problems which do exist, or they might see problems that do not exist, or they might indicate a problem which is in reality caused by some other component. They work is by checking their inputs against each other - for example, if the voltage coming from the oxygen sensor is not what it expects given where the throttle is, how fast the engine is moving, etc., it will post an error code and, in some cases, light up a warning lamp on the instrument panel.
Dealers have sophisticated computers which plug into your car's computer and can gain massive amounts of information; but backyard mechanics can also benefit from knowing what the computer thinks is wrong (since it's often right), especially given that those well-equipped dealers often have dishonest and poorly-trained mechanics.
Please read all the bullets before zooming to the codes. Thanks.
On older cars (1980s-1990s)
On newer cars (mid-to-late 1990s, 2000s):
This seems needlessly complicated, so you may simply want to invest in an OBD compatible code reader. They're not too expensive and some can record sensor readings and save them to a file (or replay them for you), making diagnosis easier. Still, it's great to be able to read your own error codes - you can troubleshoot it yourself without any tools, or you can tell when your mechanic is totally off-base.
- Codes are displayed on digital odometers on newer models.
- On many 2001 and newer models, holding in the trip odometer reset button while turning the key to RUN will start a self test, with a readout on the odometer. It will also activate all instrument panels, one at a time. We do not know if this will show computer codes, or whether it only tests the instrument panels. At the end, it may show a few odd codes that are firmware versions and not error codes.
- On most cars, the codes will read out if the engine light is on - all you have to do is put the key into the RUN position.
- Normally, to get codes, you put the key on OFF and then rapidly do OFF-ON-OFF-ON-OFF-ON (on some cars you have to do four or five, not three, OFF-ON cycles). On our test 2002 car, the key did not go back to unlock, so it was ACC-ON-ACC-ON-ACC-ON.
- You may have to have the parking brake firmly set for the codes to show! (Thanks, Steven Midway)
- Jon Yoon: The 1998 Caravan does the same check engine light code trick, but it also does an instrument diagnostic check if you hold the trip and reset buttons and turn the key to the run position and wait 5 seconds. This helped me figure out that my input and output speed sensors were broken but the actual speedometer dial could move.
- For the 1999 Jeep Grand Cherokee and up, you do the switching the key on and off 3 times, but not quickly. You turn it to on so the odometer turns on, turn it off, and then back on, wait for the light to turn on, etc. On the fourth time you'll get a code, or you'll get the word "done." (Monica MacDonald)
- A loose gas cap may light up the Check Engine light! (Thanks, Lyn Clark)
- When the computer indicates major failure, it can activate Limp In mode, which guesses about data to compensate for sensor failure, allowing you to get the car to a mechanic. One major symptom of this is the transmission sticking in second gear. This is a feature!
- 2002 Ram, put transmission in neutral, parking brake on, then do the acc-run key sequence 3 times.
- Dan Stewart wrote about the 1999+ Voyager/Caravan with digital gear selection display:
- There are 2 functions that can be accomplished with the key-on sequence. Get Diagnostic Trouble Codes by placing the key into the ignition. Push and hold the both the "Trip" and the "Reset" buttons with the left hand and turn the key to the "ACC" position (first position between "LOCK" and "RUN"). Continue to hold both buttons in and count to 5. Release both buttons, display should read trip mileage instead of total mileage. Push the "TRIP" button and the odometer will display DTC'S in rotating sequence instead of displaying total mileage.
- The second function is an instrumentation diagnostic. Place key into ignition, press and hold both "TRIP" and "RESET" while turning the key to the "RUN" position. Continue to hold both buttons in until odometer displays "CODE". Release buttons. The display will then display "999". Afterward it will display "CHECK 0" and test the analog gauges. It will then display "CHECK 1" and test the digital displays
Resetting the computer
Normally the computer will eventually reset itself; you can also use a scan tool. (See our transmission repair page for information on resetting the computer's transmission information.) Disconnecting the battery for a few minutes generally resets the computer, though it also means losing clock settings.
Sid Willoughby wrote: “To clear the check engine light on a 2002 Dodge Ram once the problem is resolved. Start the engine and drive forward then in reverse (you only have to move the truck a few feet in each direction) the turn the ignition off. Do this sequence three times. When you start the vehicle the fourth time the check engine light should go out.” (This procedure may well work on other vehicles.)
The code lists
- A common code now is P0513 - as far as we know, it just means the theft prevention system misread the Sentry Key radio code in your key (or that you put the wrong key in the ignition!). These keys were used starting in 1998.
- Click here for a 2004 computer code list, which also (for the most part) applies to vehicles made before and after 2004.
- Click here for a 2001 computer code list, which covers some vehicles from the late 1990s as well as newer ones. It shows the longer codes starting with the letter P.
- Click here for the climate control codes!
- Click here for 1980s-1990s codes. See the 2001 lists for late-1990s cars. You can find out by trial and error which list is right for you. The older codes were two digits; the newer codes start with a P and have more digits.