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Misfire CEL P0300, P0301, P0302, P0303 this morning..


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This morning, I went to top off .5 qt of oil (knew I was a little low from an oil-change a week ago). Started it up drove it out of garage onto driveway, and let it idle to warm while I run in the house to wash hands etc. Then came out and noticed the exhausted sounded weird (like misfiring), and noticed CEL was solid lite. Shut her down, check the oil cap and retighten, and restarted it, CEL still solid lite, but the car idled fine, and no misfire was felt. So I drove it into the office since I realized my Scantool is in the office...

So hooked it up and captured the following 4 codes

P0300 (misfire)

P0301, P0302, P0303

& 5 [pending] codes, not quite sure what pending means from scantool:

P0130

P1313

P1314

P1315

P1319

All looks to be from the driver side bank.. What would cause misfire to single bank when cold? Could topping off oil caused this? I was pretty sure the oil cap was tight first time around. I'm very sure Oil is clean, no intermix problems (checked coolant color the other day after changing oil, and dipstick still clean).

Car is a 99' 996 that I picked up 1.5 months ago and passed PPI from Squire Automotive. No CEL since purchase, nor any codes during PPI.

About to take car for a 3k mile trip to San Diego tomorrow.. I will bring my scan tool and keep monitoring it.. So far after clearing code, car runs good and CEL stayed off.

Edited by Zmonsta
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This morning, I went to top off .5 qt of oil (knew I was a little low from an oil-change a week ago). Started it up drove it out of garage onto driveway, and let it idle to warm while I run in the house to wash hands etc. Then came out and noticed the exhausted sounded weird (like misfiring), and noticed CEL was solid lite. Shut her down, check the oil cap and retighten, and restarted it, CEL still solid lite, but the car idled fine, and no misfire was felt. So I drove it into the office since I realized my Scantool is in the office...

So hooked it up and captured the following 4 codes

P0300 (misfire)

P0301, P0302, P0303

& 5 [pending] codes, not quite sure what pending means from scantool:

P0130

P1313

P1314

P1315

P1319

All looks to be from the driver side bank.. What would cause misfire to single bank when cold? Could topping off oil caused this? I was pretty sure the oil cap was tight first time around. I'm very sure Oil is clean, no intermix problems (checked coolant color the other day after changing oil, and dipstick still clean).

Car is a 99' 996 that I picked up 1.5 months ago and passed PPI from Squire Automotive. No CEL since purchase, nor any codes during PPI.

About to take car for a 3k mile trip to San Diego tomorrow.. I will bring my scan tool and keep monitoring it.. So far after clearing code, car runs good and CEL stayed off.

"pending" on scan tool means that the code has not yet been set, and that will normally not light up the CEL by itself, until it "graduates" to a full-blown code. The pending code is a precursor to one of the actual codes, unless the condition corrects itself while driving.

Regards, Maurice.

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OBD II Pending Codes are also referred to as “continuous monitor” and “maturing codes”. An intermittent fault will cause the computer to store a pending code in memory. If the fault does not recur within 40 warm-up cycles, the code will be cleared from memory. If the fault recurs a specific number of times, the code will then mature into a diagnostic trouble code (DTC) and the MIL or “check engine” light will turn on.

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OBD II Pending Codes are also referred to as “continuous monitor” and “maturing codes”. An intermittent fault will cause the computer to store a pending code in memory. If the fault does not recur within 40 warm-up cycles, the code will be cleared from memory. If the fault recurs a specific number of times, the code will then mature into a diagnostic trouble code (DTC) and the MIL or “check engine” light will turn on.

Golden:

Thanks for the detailed explanation!

Regards, Maurice.

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  • Admin

We still need fault codes to make any sense of the issue at hand.

Different faults require different reset/clearing/healing triggers.

From Porsche's OBD II manual...

"Fault shedding

When a fault is recognised during a diagnostic routine, it is stored as a suspected fault. At the same time, a fault shedding counter is started that contains a certain value. During additional diagnostic routines, the shedding counter will be decreased by 1 if the fault is recognised in the same area window. If the shedding counter has reached the value 0, the fault is considered as shedded.

Fault healing

When a fault is recognised during a diagnostic routine, it is stored as a suspected fault. At the same time a fault healing counter is started that contains a certain value. During additional diagnostic outines, the fault healing counter will be decreased by 1 if the fault is not recognised in the same area window. If the fault healing counter has reached the value 0, the fault is considered to be healed. If the fault has triggered the Malfunction Indicator Light (MIL) then the latter is switched off as long as it is not triggered by any further faults.

Fault erasing counter

For each recognised fault, an individual fault erasing counter is kept. The counter determines the memory storage time of the respective fault. The first time the fault is recognised, the fault erasing

counter is set to 80.

If an unshedded fault is recognised as healed, the fault erasing counter is set to 10. Each time a shedded fault is recognised, the fault erasing counter is set to 40. It retains this value until fault healing is recognised. After each warm-up operating cycle the fault erasing counter is decreased by 1, when the fault in question is recognised as unshedded or healed. When the fault erasing counter reaches the value 0, the fault is erased from the memory."

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Ah yes...The number I had was for a specific fault (which of course I can't remember)...but as Loren says it depends:

Remedying faults (CE lamp OUT)

When a fault occurs for the first time during a diagnostic routine, it

is stored as a suspected fault. In the subsequent driving cycle, the

suspicion is either confirmed (fault recurs) or cancelled (fault does

not recur, no indication on a scan tool). If the fault activates the CE

lamp, a fault correction counter is started at the same time with a

certain value (e.g. 5). In the course of further diagnostic routines, if

the fault is not present in the same range window the correction

counter is decremented by 1. If the correction counter has the

value 0, the fault is assessed as remedied. If the fault activated the

Check Engine warning light, this will be switched off if not prevented

by any further fault. The fault remains in the fault memory for the

time being and is only deleted after a number of further warm-up

cycles (defined in the fault deletion counter) (workshop assistance if

for example the tank cap is temporarily not correctly screwed in).

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oh weird, I thought I posted a reply to goldenwarrior thanking him for the link prior to my trip.. that linked helped a bunch and really gave me some confidence that maybe o2 sensor was the culprit and not something bigger.. this was very helpful especially before a long road trip..

thanks to all for the definition of pending code, i googled it after posting here and found that info too.. i never knew about pending codes for as long as i had my scantool, then again i haven't used it in 5 years or so..

Glad to update that after 1k miles in (13 straight hours yesterday to bay area, then 6 straight hours today to Irvine), the issue hasn't occurred again. As a matter of fact, car is running in top shape, with long stretches of 100+ along I-5 in mid of Cali.. Man the ROW M030 rides amazing over all types of bumps and undulation.. (side note, after living in WA the last three years, i realized how much i miss cali driving!!)

Will keep monitoring CEL and update this thread when necessary.

Hope you all had a great Christmas!

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  • 2 weeks later...

Thanks Loren, I will need to look into this VarioCam test...

I wanted to update all that after driving 3500 continuous miles over the course of 9 days I didn't experience any CEL. It seems like that was fluke, but I will plug in my OBDII reader to see if any pending codes have been captured later this week and keep monitoring it.

Thanks those that replied with useful information.

Happy New Year!

Herb

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