My jag is stil OBDI but my sister's XK is OBDII. Today at her request I installed a new purge control valve and would like to clear the stored emission codes. I don't have a code reader. The local parts store will read the codes but won't clear emission codes. Removing the negative battery cable will clear "all" codes on the XJ40 but apparently not on an OBDII car.

Anyway to clear without a code reader?

 

Disconect the negative (black) pole on the battery, and touch the cable had to the positive (red) pole. Hold for 30 seconds to allow time for the capacitors to discharge.

Then, the codes are cleared.

Autozone will always reset the codes for me if I ask. There are more than one free code checkers (national parts stores) in town.

 

That really works? I had a friend tell me the same thing but I thought he was kidding but I guess not. His version was to disconnect both cables and tough the disconnected cables together. You don't mean to touch the negative cable to a hot positive pole do you?

I went to a friend up the road that has a reader. It took several times for his reader to clear the codes. Two different readers and the little one was the one that worked best to clear out all the codes.

The CEL light is gone and I've driven the car, it has not lit for me. Hopefully for my sister it was the purge control valve I installed and the light will stay off and the gas fumes will be gone.

My next stop would have been Autozone.

Thanks for the info.

 

You can pull both cables and touch them together for a couple of minutes. It works.

Or, you can touch the negative pole to the positive pole. I agree with you that it doesn't sound right, but it still works--per one of the Jag mechanics on this website.

Or, just find another parts store that'll reset the codes for you.

Better yet, invest in a code reader for future use. I've never heard of anyone of this forum that's not glad they purchased a scanner. Just about everyone on this site has more than one car on the driveway to use scanners on--not just Jags.

Walmart.com has especially great prices on Equus Innova's with the 3030 model basic reader @ $47.54 and an advanced 3150 model (with ABS and CAN/BUS) @ $147.54. That's much less than 1/2 off.

 

There are some codes that can be cleared with battery disconnection or will clear themselves (like a lean/rich condition) after drive cycles show that the parameters are no longer in the 'red' zone, and I believe the evap codes fall into that category. Most, however, require the manual approach with a scanner so the owner takes them seriously.

 

There's no problem touching the neg. cable to the positive pole when it's not connected to the neg. pole of the batt. In other words you have no potential (voltage) when the cable is not connected to the neg. pole of the battery. You have serious problems when you connect both poles on the same battery together---at that point you have a common potential across the plates of the battery---that's a short circuit to ground. Remember never let the smoke out of the box---an old EE (electrical engr.) joke.

 

FYI
I was told by a service manager at a Honda dealer, who is sharp as a razor, that you should disconnect both posts(in case there are secondary wires), then bind them together for at least a hour, preferably overnight, so that all computers and sensors are completely drained of their back-up power and all codes cleared throughout the vehicle.
Just saying....

 

Thanks for the replies. Think I'll check out the reasonably priced Walmart code readers because the lowest price at Advance Auto was $70. I don't need them at the moment but good to have for the future. Current cars are all OBDI -

95 Caddie Deville Concours
90 XJ40
95 Subaru Legacy (17 year ol sons car)

 

ebay is a good source, just be sure to check out our Member Approved thread!