'99 Sienna LXE Code P1135/P0171/P0135

[GeneSach]

Getting all 3 of these codes at local (non-Toyota) repair shop computer check and have appointment at Toyota next Monday. The local guy sez all are related to air flow sensor issues and quoted $1,200 to replace/repair.

Sounds high to me. I'm not very mechanical but seems to me that the sensors (like the Mass Air Flow one) might be cleaned instead of replaced, no ?

Any comments on the suggested costs is much appreciated.

[SiennaDriver]

I bought an OEM Denso MAF on EBay for $60 awhile back, stuck it in myself and cured a mess of problems. Was easy.

That was a bargain price, most are slightly more.

A/F sensors can be had, Denso, for about $100 online. Google search the item number you need. The front one is easy to replace, the back one, not. It's worth it to me to pay someone to screw it in. It's not much labor time, and a lift makes it much easier.

[wiswind]

P1135 is the heater circuit of the oxygen sensor Bank 1 Sensor 1, which is the one in the exhaust manifold on the back of the motor.
This is usually a defective heater in the sensor, but check the connector to make sure that it is good.

P0171 is the Oxygen Sensor, Bank 1 Sensor 1, reporting a lean condition.
This code is usually caused by a vaccum leak......which is any air entering the intake that has not passed through the Mass AirFlow (MAF) sensor mounted on the air filter box.
This is air that the computer does not know about, so you end up with too much air for the amount of gasoline being sprayed through the fuel injectors, and a lean condition.

P0135 is the exact same thing as P1135.

I had P1155, which is the same code but for the front oxygen sensor......much easier to replace.
I have a ScanGauge and with the defective heater in my front sensor, I STILL went from open loop to closed loop within 15 seconds or so in the winter.
This means that the sensor still warmed up enough to work correctly and I had no adverse drivability issues.
Open loop is when the computer is not using the oxygen sensor input (normal until they warm up)
Closed loop is when the computer is using the oxygen sensor input.

I would get the oxygen sensor replaced and check over the vehicle to make sure that the vaccum lines are connected and that the flex line from the MAF to the Throttle body is connected, etc.
Then see if any codes come back.
At this point, those codes are not indicating an issue with the MAF.
The MAF could be cleaned with MAF cleaner.....a electronic spray cleaner that leaves no residue.