Can I ignore code P1135/1155

Tiny
TAL QUINN
  • MEMBER
  • 2001 TOYOTA SIENNA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
What will happen if I do not repair air/fuel heater sensor malfunction? I do not want to spend much on this old van. Would the fix be expensive?
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Wednesday, May 17th, 2017 AT 5:41 PM

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Tiny
CARADIODOC
  • EXPERT
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.
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Wednesday, May 17th, 2017 AT 8:38 PM
Tiny
TAL QUINN
  • MEMBER
Thanks. And is the fix a major repair, as in hundreds of dollars, or minor, as is around $100.00?
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Thursday, May 18th, 2017 AT 3:13 AM
Tiny
STEVE W.
  • EXPERT
It depends on what the issue is. Could be as simple as broken wires to the sensors or corroded connections or as bad as a failed PCM. No real way to tell without looking and testing. As for ignoring it, as Doc says, the light being on could hide something else.
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Thursday, May 18th, 2017 AT 8:35 AM
Tiny
WRENCHTECH
  • EXPERT
The 0/2 sensors have heaters built into them and the computer has determined they are not working in both sensors. If it was only one I would tend to blame a bad sensor but when it is both of them. I would first test all your fuses with a test light and look for a problem with any or the ground wire points.
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Thursday, May 18th, 2017 AT 11:35 AM

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