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Matt
Matt, Engineer
Category: VW
Satisfied Customers: 21602
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Volkswagen Jetta how do I reset the check engine light on

Resolved Question:

how do I reset the check engine light on my 1998 vw jetta 2.0 engine
Submitted: 5 years ago.
Category: VW
Expert:  Matt replied 5 years ago.
Hello

On any car if you get a check engine light or other fault light this typically means one or more of the sensors has failed or has a faulty connection.

The ECU senses this and may put the car into 'limp home' mode which typically limits the revs and the amount of power available. Usually the car is safe to drive for a short distance as the mode is intended is intended to get you home without incurring any engine damage

The quickest route to repair is to have the car plugged into a diagnostic machine which will read off the fault code stored in the ECU (providing the light is still on at this point) and indicate which sensor has failed or whether the fault is more serious.

You can do a very rough and ready check yourself by unplugging sensors one at a time and seeing if any of them change the driving condition which would indicate the most recently unplugged sensor is the faulty one. This method is not foolproof though and reading a fault code off is the better method.

You can also try resetting the car by removing both battery leads and clamping them together for 10 mins as this will reset everything so if the light re-appears then the fault is still there.
Disconnect the battery cables and clamp them together for 10 mins. Remove both battery leads from the battery then use a nut and bolt or G-clamp to hold both battery lead terminals together.

This discharges any capacitors / memory within the ECU and around the car so ensures all memory settings are wiped clear - back to the factory default.

This will reset all the systems on the car and you may need the radio security code to get it going again, and ensure that the keys are in your hand when you re-connect the battery as the car may lock and turn on the alarm
Customer: replied 5 years ago.
did as you said and the light is still on.
Expert:  Matt replied 5 years ago.
Hello

in that case the fault is genuine and the next step is to get the car plugged into a diagnostic machine to read off the fault code
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