GooOnYou

I heard that if you disconnect the positive terminal of the battery and hold the brake down it will erase the codes from the cpu. Is this true?

MazdaManiac

iTrader: (3)

Remove the negative terminal and hold the brake pedal down.
That will turn off the CEL and reset the ECU.
However, the NVRAM will retain the code in memory.
You won't see a light (unless whatever tripped the code is still in place and trips it again), but it will still be stored in the ECU and the dealer can see it.
I have yet to find a way to actually erase the NVRAM without a CAN scanner or the dealer WDS computer.

Mazda Monkey

You set a catalyst code since it was removed. If the rear O2 was not connected you also set codes for it as well. Pulling the battery will erase the codes. The NV RAM will not save the DTCs.

MazdaManiac

iTrader: (3)

This is wrong.
DTCs are stored in a NVRAM that does not require power.
They can only be erased by following the "after repair" procedure in the shop manual.
I had my ECU on the floor of my garage for several hours after setting a MAF code and it still showed up on the WDS at a Ford dealsership at which I have an acquaintance who reset it for me.
All of the emissions DTC (and probably every other DTC) can get stored.
There is a limited number of buffer slots, however.
Don't know how many right now. I'll have to set a series of CELs and see which is the first one that remains.

Mazda Monkey

Are you sure the code was not set again after the PCM was plugged back in? I have set & erased DTCs by removing the battery cable. Confirmed afterwards by WDS. NV RAM will store eccentric shaft plate profile learned by the PCM.

MazdaManiac

iTrader: (3)

Yes.
The code was caused by an interruption of the signal from the MAF which was not duplicated after the PCM was reinstalled.
The code was, however, still there.
TCS/DSC codes and all other emissions codes are also stored. This was verified by deliberately causing those codes and then pulling the PCM. They are stored even if they are only on one drive cycle and do not set an igniton switch independant MIL.

markpmm

The P0xxx code that set the CEL and the FFD will always always be in the PCM memory. The PCM may turn off the CEL but the data will be stored for future reference. U codes and B codes will clear after the problem is rectified.

drthaunghtike

i have some problems with engine check light.
one day of sunny in Myanmar country, i drove my car for about 2 hours. i suddenly found CEL was on during driving. i thought that was engine heat problem. so i shut down air-con and checked engine coolant. but engine coolant was not empty but low. so i filled engine coolant . check with OBD at local car workshop and found the problems of ignition coil #1. Error codes - U0121, U0073, P0351. but i suspected ABS problem because CEL was sometimes disappeared by popping brake pedal before starting engine. but CEL is on again now.
after that, one day of raining, i turned 90 degree from stopping position and she drifted around. fortunately car was okay but i felt so dangerous. is that usual during raining? i bought that car last year from japan.

I WANT TO KNOW .....
1. is that dangerous?
2. do and don't for that during waiting for arrival of ignition coil from foreign.

thank you. please reply me back or refer to some forum about that. i feel depression because our country has not MAZDA company.

nycgps

iTrader: (1)

holy batman ! you restored a 10 yr old thread !

change ur ignition coils first, ALL of them, oh and plugs too.

Uxxxx kind of codes are usually because something is not secured. check all plugs

ShellDude

iTrader: (12)

psst, nycgps: https://www.rx8club.com/series-i-tec...33/#post498886

he's "searching"