Check Engine Light ... but no codes?

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14,737
Location
Central NY
This was strange. Went to drive the Cherokee on Friday night (after sitting 3 or 4 weeks) and the check engine light was on. That's a problem, or so I thought, because the People's Republic of NY isn't happy if your check engine light is on and it is time for inspection. My Cherokee has to be inspected this month ... I grabbed by bluetooth code scanner, no codes stored, historic or pending. All monitors were up. Then had two different places scan the code - and same thing. No codes, pending, stored or historic and all monitors were up. So it would have passed inspection with the light on Reset the code. Light went out. Then on Saturday, the monitors all came back up. No light. Is this normal? I have never seen this happen.
 
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1,464
Location
Gulf Coast, MS
Blue tooth scanners are not extremely reliable. You might need a better scanner or possible a dealer level scanner. Worst case you take your dash board part and simply remove the light if need be.
 

Miller88

Thread starter
Messages
14,737
Location
Central NY
Originally Posted By: 3800Series
Blue tooth scanners are not extremely reliable. You might need a better scanner or possible a dealer level scanner. Worst case you take your dash board part and simply remove the light if need be.
I had it scanned by two others with 'real' scanners. Same result.
 
Messages
36,471
Location
ME
Maybe it was complaining about something not on the emissions list, like no data from the body module or ??? Though I would expect the feds would be all over them to have the CEL mean emissions and only emissions, and to come up with another light for other problems. Can you do the key flick on this to get codes on the odometer? Too late now, I guess. wink I can make my HHR throw a misfire code by cold starting it and running the heat on super-high, it draws too much heat from the engine. It clears right up. Though the OBD doesn't start counting misfires until a minute in, maybe your extended downtime made it a little crotchety for the first couple minutes.
 
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5,722
Location
Charlotte, NC
Low battery voltage. All my old mopars will do that from time to time. Usually the battery just needs charging or the terminals need cleaning, but it could be poor grounds or the battery or alternator. Wayne
 

Miller88

Thread starter
Messages
14,737
Location
Central NY
Originally Posted By: Oldmoparguy1
Low battery voltage. All my old mopars will do that from time to time. Usually the battery just needs charging or the terminals need cleaning, but it could be poor grounds or the battery or alternator. Wayne
That one makes sense. This vehicle has a parasitic draw. Has since I have owned it. Some day, I will find it. Usually 4 weeks is about as far as it can go before completely discharging the battery.
Originally Posted By: eljefino
Maybe it was complaining about something not on the emissions list, like no data from the body module or ??? Though I would expect the feds would be all over them to have the CEL mean emissions and only emissions, and to come up with another light for other problems. Can you do the key flick on this to get codes on the odometer? Too late now, I guess. wink
Any code will fail - Had a 2004 Wrangler that failed for .... battery temperature sensor ... Luckily it was warrntied. I am supposed to be able to get the codes to display with the key ... all I can do is get the gauge self test.
 
Messages
5,651
Location
Iowa
Originally Posted By: Miller88
Originally Posted By: 3800Series
Blue tooth scanners are not extremely reliable. You might need a better scanner or possible a dealer level scanner. Worst case you take your dash board part and simply remove the light if need be.
I had it scanned by two others with 'real' scanners. Same result.
Were the "real" scanners just ones that your friends own? Some may not read the manufacturer's specific codes. You don't necessarily have to go straight to the dealer to get those codes read as a good mechanic should have the equipment to do it. My Snap On Solus Ultra has software to read any code and test most functions. Bottom line is that the typical hand held scanner won't always have the software to get the job done.
 
Messages
1,462
Location
East Mountains, NM
Originally Posted By: Oldmoparguy1
Low battery voltage. All my old mopars will do that from time to time. Usually the battery just needs charging or the terminals need cleaning, but it could be poor grounds or the battery or alternator. Wayne
Winner winner, chicken dinner! All that has to happen is for the voltage to drop too low during cranking. It can take 100 miles and multiple starts for it to reset itself, if it even will.
 
Messages
5,722
Location
Charlotte, NC
Originally Posted By: Miller88
Originally Posted By: Oldmoparguy1
Low battery voltage. All my old mopars will do that from time to time. Usually the battery just needs charging or the terminals need cleaning, but it could be poor grounds or the battery or alternator. Wayne
That one makes sense. This vehicle has a parasitic draw. Has since I have owned it. Some day, I will find it. Usually 4 weeks is about as far as it can go before completely discharging the battery.
All mopar OBT-1 ECU's will do this. Won't set a code. I don't know about OBT-II, but that would be my first thought. Wayne
 
Messages
3,858
Location
Cape Cod, MA
Originally Posted By: Miller88
No codes, pending, stored or historic and all monitors were up. So it would have passed inspection with the light on
Not in MA. Here, if the light is on for any reason it's an automatic fail. If you're lucky, the station won't start the process if the light is on, giving you a chance to fix it without having a "failed emission" sticker with a big R on your windscreen.
 
Messages
6,164
Location
Illinois
I had a Taurus that the CEL would come and go on it when highway cruising. It would never set a code or stay on continuously. I finally pulled the plugs and one was white, meaning a really lean mix. I swapped out the fuel injector and all was well again.
 
Messages
220
Location
Massachusetts
Originally Posted By: babbittd
It's interesting that no codes were retrieved, but using the reader to reset the codes worked to deactivate the CEL.
Is it possible that there was a Chrysler specific code that certain generic OBD-II devices would not be able to interpret? I'm hoping not to scare the OP, this is now more of a general question about how the code readers operate.
 

Miller88

Thread starter
Messages
14,737
Location
Central NY
Originally Posted By: babbittd
Originally Posted By: babbittd
It's interesting that no codes were retrieved, but using the reader to reset the codes worked to deactivate the CEL.
Is it possible that there was a Chrysler specific code that certain generic OBD-II devices would not be able to interpret? I'm hoping not to scare the OP, this is now more of a general question about how the code readers operate.
It could be a code for NSS or something. As long as I can get an inspection sticker, I'm happy.
 
Messages
36,471
Location
ME
Originally Posted By: babbittd
Originally Posted By: babbittd
It's interesting that no codes were retrieved, but using the reader to reset the codes worked to deactivate the CEL.
Is it possible that there was a Chrysler specific code that certain generic OBD-II devices would not be able to interpret? I'm hoping not to scare the OP, this is now more of a general question about how the code readers operate.
As I understand it, emissions required codes must be "in the clear" to consumer code readers and in the P0xxx series. They're allowed manufacturer specific codes to enhance the clarity of what is described, in the P1xxx series. For example my lazy o2 sensor triggered both a P0133 and a P1xxx something or other. So I agree that's it's possible, though it smacks of misuse of the CEL, and an odd interpretation of implementing the law.
 
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