Expert: Sean Halliday - 6/24/2006

Question
Hi, My 1994 Geo Tracker engine "blew" -meaning that it threw a rod or ?which went through the oil pan.Naturally the check engine light came on. The engine has been replaced with another used engine but the check engine light won't go out.

Should the "check engine" light reset itself after the new engine is installed.?A mechanic told me that all Geo engines before 96 or 98 should reset themselves but those after that date will need to have codes reset to extinguish  the light.

Any thoughts on this pro blem? THANKS.
Jertwr@yahoo.com  

Answer
yes ,,before OBD2(pre 1994) most cars can be reset by disconnecting the negative battery terminal,,,for 30 secs thats for intermittent codes but you will probably have a "hard"code which will need read and the fault repaired or the light will keep coming on.on your car use a jumper wire to bridge terminals 2 and 3 of the ECM connector located in the engine compartment near the battery its got 4 terminals should look like a small cube,,,when you bridge it the check engine light will flash on the dash,thats with ignition on and engine NOT running,the flashes will read ,long flash is 1,short ,,,2,3,etc,,eg,one long 3 short is 13,2 long 4 short is 24,,and so on,,,,you will need to get a code book to determine what code you have ,when you get the code clear it after you fix the problem,,which ever sensor is faulty, by removing the tail light fuse or disconnect the negative terminal for 30 secs.if you dont have a book just email me the codes you get and i will let you know what the fault is,,,,,,