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How-to: Check your own OBD codes

The people who engineered the Neon were apparently bright enough to realize that the type of people who would be buying their cars would be too poor to take them into the stealership every month when the check engine light comes on and pay good money to have some kid plug in a computer and press the green button to see what went wrong. The ability for the Neon to flash the OBD codes to anyone who can cycle the key on and off three times and can count is perhaps this cars only redeeming quality. If you can cycle an ignition key on and off three times without starting the car and shutting it off three times, know how to count, and know how to read, then you too can troubleshoot your own OBD codes.

Notice: If you bought your Neon used and never see the “Check Engine” light come on, even when first starting the car, then odds are good that someone removed it.

Step 1: Within 5 seconds, cycle the ignition key on and off three times. That's on-off-on-off-on. Leave it on at the third cycle. Please note that “On” doesn't mean “Start.”

Step 2: The “Check Engine” light will start flashing. No, the bulb isn't starting to burn out. The code is represented by the number of flashes. There is a pause between the flashes. There are two numbers that represent each code. So if it flashes one time, pauses, two times, pauses, five times, pauses, five times, pauses, then it doesn't flash anymore, that means you have code 12 and 55 stored. Kind of like morse code.

Step 3: This time, get a pen (or pencil) and paper and repeat step 2, because you forgot what codes were stored. Write them down this time.

Step 4: When you get the codes, you can look up what they mean in the handy-dandy table below. Consider printing it out and keeping a copy in your glove box. With a Neon, it will get used a lot.




Timing belt skipped 1 tooth or more from initial learned value; Intermittent loss of either camshaft or crankshaft position sensor; No crank reference signal detected during engine cranking


Direct battery input to PCM was disconnected within the last 50 key-on cycle


No change in manifold absolute pressure (MAP) from start to run


Manifold absolute pressure (MAP) sensor voltage out of range


No vehicle speed sensor signal


Closed loop temperature not reached or engine cold too long


Oxygen sensor problem, downstream or upstream


Engine coolant temp sensor out of range


Intake air temp sensor out of range


Throttle position sensor (TPS) out of range, or disagrees with MAP


Idle air control motor circuits problem, target idle not reached (+/- 200), vacuum leak found


Injector control circuit problem


Evaporator purge flow monitor failure or evaporator solenoid circuit problem


Exhaust gas recirculating (EGR) system failure or solenoid circuit problem


A/C clutch relay circuit problem


Speed control solenoid circuits problem


Radiator fan control relay circuit problem


Torque converter clutch solenoid circuit or park/neutral switch failure


Generator field not switching properly


-Fuel pump relay control circuit problem
-Auto shutdown (ASD) relay control circuit problem
-No ASD relay output voltage at PCM
-Fuel level sending unit - volts out of range
-Fuel level sending unit - no change over miles


Single/multiple cylinder misfire


Battery temperature sensor volts out of range


Charging system voltage too high


Charging system voltage too low


Fuel system lean


Fuel system rich


Internal controller failure


No cam signal at PCM


End of error messages (If you get only this, no errors were found)


PCM failure - SRI mile not stored


PCM failure - EEPROM write denied


Catalytic converter efficiency failure


Power steering switch failure

Step 5: If you have no idea what an oxygen sensor, PCM, or EGR valve is, you should've stayed in school a little longer and took some auto shop courses. You'll have to take your car to a mechanic now and shell out hundreds of dollars to get something fixed that might otherwise have cost you fifty bucks and a couple of hours. The mechanic stayed in school and doesn't have to drive a neon.

Step 6: Know what your doing, fixed the problem, but the light won't go out? Disconnect the battery for a couple of minutes. Or longer, or less. However long it takes to clear the code. When you reconnect the battery, the check engine light should be out.