pezdespencer

I just took my 1999 Honda Accord EX V6 to get the emissions tested and it failed. It showed P0420 and P1259, and the check engine light failed to turn on. Is there anything that could cause both of these codes? I just removed a subwoofer and it is possible that I disturbed some wiring while pulling out the leads between the battery, stereo and subwoofer. Any thoughts?

MAD_MIKE

Ignore P0420 for the moment.
Fix the CEL lamp first, even if there are no codes the CEL lamp not working is an automatic fail.

Verify that it is only the CEL that is not working. All warning lamps should turn on initially when the key is turned to II(ON). If not there may be other problems with the gauge cluster. If only the CEL lamp, replace the lamp and retest.

P1259 has to do with VTEC oil pressure. If there is low oil or not enough pressure the VTEC oil switch will not allow VTEC actuation and will limit power of the engine.
If you have an oil leak, fix that first.

Clear codes. start engine and allow it to fully warm up, two radiator fan cycles. Place the transmission in first and drive holding the engine at 4Krpm for at least two seconds. Do this two more times. If P1259 does not come back, mot likely an intermittent fault. Check for loose corroded electrical connections.

If it does come back, post back here for full diagnostics.