View Full Version : Code 51, 66, and 91?

06-28-2003, 07:25 PM
what do these codes meen? how do i fix them?

Randy N Connie
06-28-2003, 07:49 PM
I don't know what is wrong with your car,but here is what
the codes are.

51, coolant temperature sensor circuit open.
Do you have it full of anti freeze,the wires all hooked up,
cap and wires on the overflow tank.

66, Mass air flow sensor circuit out of range,low.
You could make sure the small wires are clean in the MAF.

99,Oxygen sensor indicates system lean,left side.
How old are both the o2 sensors,maybe they need to be replaced.

If you could list more about your problems.Maybe someone that
knows more about SCs,than I do would respond.

I would replace both 02 sensors,if they are old.

good luck RANDY

06-28-2003, 08:05 PM
02 sensors are new(less than 5000 miles on them), but havnt replaced since the headgaskets blew?

i just put in a new coolant temperature sensor, but the light in the dash says low coolant level

how abouts do i clean the small wires in the maf?


Randy N Connie
06-28-2003, 08:38 PM
Unplug the MAF take the two top screws out, carefuly pull the
sensor out.you will see two small wires.clean with alcohol and
a Q'tip. Be very careful not to bend the wires.

If you blew the head gaskets,and got anti-freeze on the 02s.
you may need to replace the 02 sensors.They don't like anti-freeze.

If you have a bad 02,it may be on the same side of the motor that blew
the head gasket.