Pending codes and DTCs?

When reading codes from your vehicle the fault code reader may show them as pending codes or normal Diagnostic Trouble Codes (DTC).

Pending codes (also known as continuous monitor codes) will be registered when an intermittent fault occurs. If that fault does not happen again after x number of start/stop cycles, the ECU will erase the code from memory. If the fault is persistent it becomes a DTC.

If you have read pending codes it is advisable to check the codes again after a week or so.  If there is no apparent problem with the vehicle it is safe to erase the codes too and check back. But always make a note of any fault codes with the date and mileage of a vehicle.

If the codes read include a DTC then you need to investigate further. This you can either do yourself or advise your garage. If, again, you don’t see an apparent problem (depending n the severity of the code) with the vehicle you can note the codes down and erase them. Then check again after a week or a few days depending on how often the vehicle gets used. If a repair has been made (previous owner) the DTC may just not have been reset after the repair.

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2 Responses to Pending codes and DTCs?

  1. Barbara Cook says:

    I recently went in to get my state inspection which I passed. The next day my engine light went on. I took it back to the dealer and after 1hr, they said I had a cracked flex pipe. I asked how that could be if I passed the emissions yesterday and they told me I must have cracked it the next day. That iS impossible as I only used the car to get gas. But, I was leaving on a road trip so I had to fix it. Fast forward a week, and on my way home my engine light went on. I went to an auto store and had a diagnostic scan done in 5 minutes and found it was a sensor that needed fixed before my next inspection. I think I was duped by my dealer I doubt I ever had a cracked flex pipe is there any way I can find out?

    • FCR1 says:

      Hi Barbara,
      Apologies for the late reply. Hard to find out after the replacement. It could be it didn’t need to be or was just incidentally found to be cracked and not relevant to the engine light.
      Best to buy a fault code reader and check for yourself. They’re not expensive and most times the engine check light is nothing serious.

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