Is there a way to use an OBD scanner without the engine running? The jeep cranks but won't run, and we're trying to determine the cause. Thanks

 

should just have to turn the key to the run position

 

Yes, you can scan for codes with a code reader or a scan tool with the key in the ON position.

Engine does not have to be running.

 

Thanks. Has anyone tried using the ignition code trick, the thing where you flip the ignition on 3 times and then the check engine light flashes the code?

 

Retrieving OBD codes on the Jeep Cherokee (XJ)

OBD1 Models: 1991-1995
1) Start engine (if possible). Move transmission shift lever
through all positions, ending in Park. Turn A/C switch on and then off
(if equipped).
2) Turn engine off. Without starting engine again, turn
ignition on, off, on, off and on within 5 seconds. Record 2-digit
fault codes as displayed by flashing MIL.
3) For example, fault code 23 is displayed as flash, flash,
4-second pause, flash, flash, flash. After a slightly longer pause,
other codes stored are displayed in numerical order. When MIL begins
to flash fault codes, it cannot be stopped. Start over if count is
lost.
NOTE: A "5-5" will always occur to signal the end of the sequence. Some will flash the "1-2" code indicating a recent battery disconnect even if you haven't done it. Ignore these two codes, and mark down all others.

OBDII models (1996 and “SOME” 1997 models) Put the key into the ignition, push down the odometer reset button, then turn the key to RUN with your finger on the button - and then release the button. The odometer will go through 1111111 through 999999, then display the car's serial number. It will then show the 2 digit error codes. A "5-5" will always occur to signal the end of the sequence. Some will flash the "1-2" code indicating a recent battery disconnect even if you haven't done it. Ignore these two codes, and mark down all others.
The 2 digit code is helpful, but it is not as specific as the full PXXXX code, which is only available using a code reader or scan tool, so generally I recommend using the code reader or scan tool. But if you have a CEL and don’t have access to a code reader or a scan tool, try the odometer technique to point you in the right direction until you can gain access to a code reader or scan tool.

Note: The above OBDII odometer technique works only for 1996 and early 1997 model XJs, so while it might work on one 1997 XJ, it might NOT work on another! Once Chrysler made the change during the 1997 build year, for anything built after that date through 2001 you will need either a code reader or a scan tool to retrieve the codes.

 

Does that work on the OBD2 models? I used to have to do that on OBD cars. These days I use an OBD2 Bluetooth scanner with Torque on my Android phone. The scanner's only like twenty bucks on Amazon, I'd recommend it if you have a smartphone!