My 97 gave me 4 codes when I did the key on off trick. They were 12, 21, 21,55. I checked the list on this site and am having tough time deciphering. Please help!
Error code explanation?
- Thread starter Brian 97 TJ
- Start date
12 and 55 are common, don't worry for now.
The 21, 21 codes are 02 sensor codes.
It's telling you it needs 2 new precat NTK 02 sensors for your 4.0
Piggy back off this OP, our 4.0s are picky about 02, don't get a Bosch or a store brand. NTK is the ones that work and they're not overly expensive.
This is why I prefer an actual OBDII scanner 
X2 to this. You'll regret not getting an NGK / NTK O2 sensor.
See here for more on that:
The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread
X2 to this. You'll regret not getting an NGK / NTK O2 sensor.
See here for more on that:
The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread