Looking for some help with misfire codes on a 2001 Discovery II.

Had P1412 and P1415. Mechanic checked it out and all looked okay, but he replaced a few fuses. He also replaced the Crank Position Sensor, which he tested and was bad. A day later, the codes were back.

Not only that, only drove about 10 miles and noticed the car was very sluggish, slow to accelerate and the service engine soon light was on and blinking. When I got home, now have 5 codes: the already existing P1412 and P1415, but now P0301, P1300 and P0306.

Mechanic is not open on weekends, so trying to figure this out over the weekend, if I can. I suspect it has to be something that the mechanic did not re-install correctly that is allowing an air leak? Seems too coincidental for something new to have gone wrong after only driving 10 miles after service.

Any insight?

 

Do you have a copy of the RAVE factory service manual?

RAVE shows this for the first two codes you mentioned.

P-code Description
P1412 Secondary Air Injection System – Malfunction Bank 1 LH (Insufficient SAI flow
during passive test)
P1414 Secondary Air Injection System – Low air flow Bank 1 LH (Insufficient SAI flow
during active test)
P1415 Secondary Air Injection System – Malfunction Bank 2 RH (Insufficient SAI flow
during passive test)
P1417 Secondary Air Injection System – Low air flow Bank 2 RH (Insufficient SAI flow
during active test)

RAVE also says "NOTE: A malfunction of the SAI pump powerstage is logically expected to result in both engine banks reporting the
same fault."

Do you know what exactly your mechanic did when you say "Mechanic checked it out and all looked okay, but he replaced a few fuses."? Did the mechanic say he checked the SAI system? Is a Land Rover specialist who knows the Disco SAI system faults and their remedies? (I do not; my truck doesn't have SAI, thank God.)

I don't know for sure whether or not an SAI malfunction can result in the P03xx misfire codes, but I do recall that the SAI is supposed to operate for only the first few minutes after a cold start. You might try driving it until the codes appear, then clear them and see if the rough running continues and the P03xx codes return in the same drive cycle. If they do return it would seem the two sets of codes may be unrelated. I they do not return that would point back to just the SAI problem that needs to be diagnosed.

In any case, a flashing SES light means catalyst-damaging misfires (i.e. too much unburned fuel that will eventually damage the cats. Don't drive the truck for any extended period with the flashing SES. I'm suggesting just a relatively short drive for the diagnosis only.

 

I've had these codes. Not sure it's exactly misfire. Although is SAI system. Insufficient flow can be for all kinds of reason, so it's a generic code.

My fan/pump was a howler. I tried to repair it, in the end had a 2nd hand one sent from a yard. Was quieter but not the cause of the codes.

I looked around for vacuum leaks from the usual suspect spots. Swapped some old looking tubes out. Wasn't the cause.

Swapped the SAI pump switch out. Was the cause. My switch wasn't switching things on and off properly. Trace your sai switch, passenger side, take it off, and give it 12v direct. You should get a very pronounced click. Mine was a kinda lazy, fat, tap. Not a click at all.

Swapped it, all good. Takes 10 minutes or less once you have it in hand.