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Clearing stored error codes with OBD reader

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I suppose I've done well to get to 45 months of ownership and 36k miles covered before suffering my first 'beat missed'.

As it was a nice afternoon, I decided to take the Evora for an extended blast around the countryside. About an hour (and 50 or so miles) in and almost home again, right in the middle of an overtake, it happened. I was pushing through 5k revs when the car gave a sudden lurch, throwing me against the seatbelt, the engine note changed noticeably from the usual bellow of the 2bular to a harsher raspy sound, then it wouldn't rev beyond about 4k and the dreaded amber 'engine of doom' light appeared in the instrument cluster.

It sounded like it was then running on only 3 cylinders but felt more like it was only using 1, the power delivery was so weak, but I managed to limp home the final couple of miles despite the engine trying to cut out every time I dipped the clutch, with the idle falling to a very lumpy 500 or so rpm. I had bought an OBD reader some time back but had never used it (or any other similar device) before tonight, in fact it was still sealed in its packaging. A quick read through the instructions and it was plugged in to reveal a stored code of P1302 and 2 pending codes, P0300 and P0301.

I was all set to erase the codes and see what happened after that when I spotted the following paragraph on the next page of the leaflet:

"CAUTION: Erasing the Diagnostic Trouble Codes allows the scan tool to delete not only the codes from the vehicle's on-board computer, but also Freeze Frame date and manufacturer specific enhanced data. Further, the I/M Readiness Monitor Status for all vehicle monitors is reset to 'Not Ready' or 'Not Complete' status. Do not erase the codes before the system has been checked by a technician."

Is this something I should be concerned about (i.e. leave it well alone and seek professional help after the festive season) or should I just push the button and cross my fingers

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David. I think in this case you should err on the side of caution and wait for someone who knows better before going for the push the button option.

:sofa:

 

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Have you had a good look round the ignition system? Could be a simple fix and the fault will clear. 

Have cleared faults without issue before using a Bluetooth OBD reader but don’t know what the paragraph is on about. Having said that I never read the instructions. 

Googled it, https://www.obdautodoctor.com/scantool-garage/obd-readiness-monitors-explained

 

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That paragraph does sound a bit extreme. I’ve never had any issues with an OBD reader/eraser in the past. 

Can you delete the codes individually?

Incidentally, what do the error codes that you got refer to?

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12 hours ago, Alan H said:

Have you had a good look round the ignition system? Could be a simple fix and the fault will clear. 

Not as yet. It was getting dark by the time I got home last night and we've got folk round for Christmas lunch, not that that will stop me going for a look around the engine bay late whilst they're in 'digestive' mode.

 

4 hours ago, Bravo73 said:

Incidentally, what do the error codes that you got refer to?

P1302 is for "a misfire causing catalyst damage", P1300 is "a misfire, multiple cylinders" and P1301 is "a misfire, cylinder #1", which presumably would be why it went into fail-safe limp mode and shut down one bank of cylinders.

Here's hoping it's something simple to spot and fix, or even better just a sensor glitch which fixes itself - don't want to be Lotus-less until next year, :cry:  - I'm off for the next 10 days and was really looking forward to several sessions of converting hydrocarbons to noise and motion.

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As above, I’d have a look around the ignition wiring for cyl 1 also checking the coil pack and sparkplug if you can. An excellent opportunity to enjoy a glass of port on your own. 

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I went out a couple of hours ago and checked the car again. Still idling like a bag of nails with the MIL on so shut it down. I decided to throw caution to the wind after reading the link posted by @Alan H and realising that the readiness status monitor warning wasn't the big issue being projected by the instructions.

The plugs and coil packs were changed at the last service (7 months and 5k miles ago) so I was quietly confident that they would be OK. After a poke and prod around the electrics, disconnecting what I could and giving everything a spray with contact cleaner, I went for broke (having decided to throw caution to the wind after reading the link posted by @Alan H - thanks for that, :thumbup: ) and cleared the error codes.

Moment of truth and she fired straight up into a nice even 6-cylinder idle with the MIL extinguished and a few prods on the loud pedal (after letting things warm up a bit first of course) showed that normal throttle response has been restored, although I'm not sure the replete relatives snoozing it off in front of our open fire appreciated the glorious exhaust barks as much as I did, :whistle:.  I'll take her out tomorrow and conduct the 'drive cycle' as described in Alan H's link to restore the status monitors but for now it's looking "all systems go!"

Happy bunny (for now at least) so off to raid the fridge for some Christmas cheer, :cheers: .

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DONT CLEAR THE CODES! 

 

Excellent. 😆 

 

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Glad the car is working fine now.   

I had a similar problem in the summer, was just driving along, highish revs and then a rough sounding engine. I think I got error codes: Misfire causing catalyst damage and misfire on cylinder 5.  It sounded rough after a few restarts but soon coughed it out it’s system and was fine after that.  

I took it into Hoffmans to get a check up but they said it was fine. Their diagnosis systems didn’t detect anything.  Many many miles of ragging the car later and I haven’t had an issue.

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Generally it makes sense to clear the faults on forst occurance. This is what your dealer will equally do. 

However, don't do it repeatadly on the same errors (unless they are very rare), that is when it is time to go to the dealer and have him fix it.

Many faults are cleared on restarting the engine, or after a few cycles without fault.


If you have the choice between a Stairway to Heaven and a Highway to Hell don't forget the Nomex®!

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I had this on my Exige V6 and after plugging in the OBD reader, deliberated for a while about deleting the codes. Eventually I thought what the hell, what can possibly go wrong?

Anyhow, codes cleared, the engine started and ran just fine thereafter and the problem never reoccurred during my last 18 months of ownership. 

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