1999 Accord w/3 engine codes
 

OK guys, I need a little help. Check engine light came on. Checked for codes and got the following in this order:
P1259, VTEC System Malfunction
P0171 Fuel System Too Lean
P1456 Evaporative Emissions (EVAP) Control System Leakage (Fuel Tank System)
Where do I start?

P0171 is the most serious. I suggest addressing this first. If you can monitor fuel trims, look for fuel trim to possibly reduce under a sharp throttle increase. If yes, then a vacuum leak is likely. Other possibilities are fuel injector partial blockage, low fuel pressure (blocked fuel filter or weak fuel pump)l.

P1259 is a Vtec pressure switch circuit or Vtec solenoid circuit fault. Aggravating but not detrimental to engine health. Possibilites are bad switch, bad solenoid, wiring/connector fault, or ECM fault.

P1456 is evap system leakage. Can be as simple as loose fitting gas cap, but lots of other possibilities. May require a smoke machine to locate leak.

good luck

Just me but the 1259 could be an issue.....LOW OIL LEVEL, at least check the oil level before starting anything.

Oil level is full. That was the first check.
How do you monitor fuel trim?

Is this a four or six cyl car?

There are scan tools that will allow you to plug into the OBD port and read them.

Again, just me but I would want to solve the 1259 :shrug:

4 cylinder car. Cleared the codes and they haven't returned. I think there is a problem when the car runs in traffic on the highway. Doesn't the VTEC lean out the engine to get better gas mileage on the highway. The light has only come on twice but both times when the car has been on the highway. First time after exiting the highway the other in stop & go highway traffic.

Vtec opens to improve engine breathing above 3000 rpm. Most highway cruising is under 3000 rpm.

When/if code/s return, scan them as soon as light turns on to see what code/s are presented.

good luck