P1135 - O2 Sensor Heater Circuit Low Voltage (Bank 1 Sensor 1)
P1155 - O2 Sensor Heater Circuit Intermittent (Bank 2 Sensor 2)
Your code description is wrong. These refer to two of the oxygen sensors, and since they are involved with emissions, they will turn on the "check engine" light. The first code means the engine computer will not be able to fine tune the fuel/air mixture on one side of the engine. The second code means that oxygen sensor will not start taking readings until the heat of the exhaust gas gets it up to 600 degrees, just like on much older cars. The heater circuit gets it up to 600 degrees faster so it can start reporting the conditions sooner.
Neither of those codes refer to something that you should notice as far as engine performance. Fuel mileage will suffer, but there is a bigger problem. Your engine computer can detect well over 2,000 defects, and set fault codes for each of them. Many of those defects are very minor with inexpensive fixes, but if ignored, could turn into expensive problems and/or miserable engine performance problems. You will never know if one of those minor problems occurs because the "check engine" light will already be on. Also, there is always a long list of conditions that must be met for a fault code to set, and one of those conditions is that certain other codes cannot already be set. Those other codes are for circuits the computer uses for reference or comparison, or when one defect can be expected to cause other defective conditions. Having these two codes set already will stop some tests from being run, so some defective conditions won't be detected, that is, until you have these current problems fixed, then the other tests will resume. That is when any new or additional problems will show up as new fault codes. The longer you wait to solve the current problems, the more time there is for additional problems to develop.
Saturday, November 24th, 2018 AT 8:09 AM