Question

2002 GMC Envoy with engine codes P0135 and P0440. What do these codes mean?

Answer 1

P0440 Evaporative emission control system malfunction

This deal with the purge control system, where the EVAP system is unable to achieve the calibrated amount of vacuum level. There are 2 known cause that this code condition creates, the engine is hard to start after filling the fuel tank, hard to start at times. what happens is the purge valve sticks slightly open and the only remedy is to replace the valve.

Answer 2

P0135 GMC Code - HO2S Heater Performance Bank 1 Sensor 1
Read more: https://www.autocodes.com/p0135_gmc.html

P0440 GMC Code - Evaporative Emission System
Read more: https://www.autocodes.com/p0440_gmc.html