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cel codes po301, po302

1.2K views 6 replies 7 participants last post by  WTS  
#1 ·
Can anyone tell me what might be wrong with my 2000 spyder? About two weeks ago my cel came on and took it to autozone and pulled two codes po301 and po302. It was tuned up last year, so I cleaned maf, and reset the ecu. It came back on shortly after, so I took it to the dealer and they said it was the ecu. I found out today that even after they replaced the ecu with the updated version that it was doing the same thing. Any insight would be appreciated.
 
#3 ·
when there was something wrong with my ecu, it would not even pull up any codes. light would come on, but no codes would come up. it ended up being the ecu got wet because the drains in the sides got clogged and flooded the compartments behind the seats, and got the ecu wet.

anyway, you are getting misfires .
 
#4 ·
I kept getting the p0300 code then took it to toyota, they found nothing wrong with it so they replaced the ecu (TSB) a couple of months ago. I've had the P0300, 301, 302, etc even after the new ecu but still have yet to actually here knocking. I've checked, double checked, O2 sensors, maf sensor, and ppe resistors, spark plugs, and checked for vacuum and exhaust leaks and came up empty. I've decided to live with it and keep my obd reader in the glove compartment for resets.
 
#5 ·
funny you should bring that up because i had the same problem about a couple of years ago and toyota replace the ecu and now the problem is back. i have taken it to Ammco and they have reset it several times but the codes don't go to anything. i'm lost as well.
 
#6 ·
obd codes

I have spent quite a few dollars in the persuit of knowledge where it comes to the codes! I now have a technician book for odb systems. Applications covering 1990 through 2002.

I have the codes and the pin voltage tables for all the toyota line here in the us.

In reference to the P0300 code - 1T / 2T catalyst emission code for all models 1994-2002, Detailed as a multiple cylinder misfire condition. No PCM codes set, engine running, VSS input over 3 mph, and the PCM detected a misfire in multiple cylinders in the 200 or in the 1000- rpm revolution period.

Now here is the interesting thing....

The codes P0301 through P0308 are the same thing except the last digit correlates the cylinder at fault. IE. P0301 is cylinder one misfiring.

Anyone out there wanting further information, I would be happy to type this information along however due to the nature of copyright laws Im unwilling to copy or exact replicate or transmit.

I have diagnostic procedures.
I have the Pin connector breakdown and voltage tables.
I have the code list.
I have the PID data.
 
#7 ·
Is there ever a P0300 or is it always those two specfic cylinders?
When does the CEL come on? at idle , steady throttle cruising or when accelerating hard?

Lots of things can cause mis-fires.
1. Bad gas
2. Dirty air filter
3. Dirty Maf
4. Dirty/worn spark plugs
5. Coilpack - try swapping 1 to 4 and see if you get a P0304 instead of 301
6. Fuel Injector
7. ECU - THe early firmware reported more misfires - There's a reflash.
8. Vacuum leak - Got a CAI? Revert back to stock and see if it stops.
9. Missing Pre-cats - take out the O2 sensors and LOOK for honeycomb.
IF all you see is a black hole then its bad news for the engine.
10. Clogged main cat
11. Fuel pressure (too high or too low)
12. Low compression
13. Damaged valves