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Toyota Sienna CE, 2001, Oxygen Sensors

I have a 2001 Toyota Sienna CE with engine codes P1135 and P1155. I am looking for a way to bypass the oxygen sensors, as well as suggestions regarding the lack of engine power.

As long as it is slowly accelerated, it can do OK. But if accelerated too quickly, it bogs down. And when it goes up a bridge, it will slow down by

10-15 mph.

From the information that I've found on the web, the codes should not cause the engine to run as it does. This is because the oxygen sensor heater circuits will not influence the car computer - it is merely an open heater circuit. The purpose of the oxygen heater circuit is to heat up the oxygen sensor when the engine is first turned on to warm it for accurate cold running operation and input to the vehicle computer. Once the engine is at operating temperature, it is basically useless.

The main issue is this:

When the car is put in drive, it seems to bog down if given too much acceleration (gas) at one time so an easy, steady touch as you accelerate is needed to gain speed. It could take one mile to get to 40mph sadly. Going up bridges is terrible because it seems to choke up and struggle and drops 10-15 mph in speed. Once up to 40-50mph on flat road, it runs good, can get to 60mph if work at it. If you take off slowly and gradually increase speed, it seems to run fine just so slow to accelerate with power.

The codes indicate an issue with the oxygen sensor heater circuit but online discussion consensus would indicate that the heater circuit should not influence engine management and the running of the engine.

I took the van to Aamco and was told that it is definitely not the transmission.

On Toyoto Sienna's prior to 2001 there was a serviceable fuel filter external to the fuel tank. From 2001 on, the filter is in the fuel tank. I do not have a pressure gauge to measure the fuel pressure out of the fuel pump so I do not know if the filter in the fuel tank is clogged.

There are 3 catalytic converters on this van with a V6 engine.

The codes do not specifically indicate an oxygen sensor failure, only an oxygen heater circuit failure. I do not know if there would be another specific code for a failed oxygen sensor or if the oxygen heater circuit failure is a catch-all for any oxygen sensor problem.

I have found online oxygen simulators that can be spliced into the oxygen sensor wiring to simulate the proper operation of the oxygen sensor and preclude the reporting of the sensor error code.

Thanks, Adam

Reply to
Adam Bomb
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P11345 and P1155 refer to an air/fuel sensor heater failure. An air/fuel sensor's purpose is basically the same as an oxygen sensor's purpose and is mostly used in vehicles with California emissions. The parts are not interchangeable.

There is no legal way to bypass an oxygen sensor or air/fuel sensor. Proper diagnosis of P1135 and P1155 requires digital multi-meter.

The lack of power when accelerating could but is not likely to be related to the air/fuel sensor heater problem, so proper diagnosis starts with the basics.

A clogged fuel filter is not a likely cause as they are generally good for the life of the vehicle unless the fuel was contaminated.

How many miles are on the vehicle and what is its service history?

Check the condition of the engine air filter and spark plugs. Check to see if proper plugs were installed.

Check for an obstruction inn the exhaust system, especially if the vehicle has high miles or has an aftermarket exhaust component.

Check for leaks in the air intake tube between the air filter and throttle body.

If the air filter is very dirty, try a shot of electronics cleaner in the MAF sensor opening.

Check to see if the throttle position sensor has been disturbed.

Reply to
Ray O

The Sensor Heater Failure does not mean the sensor does not work, it only means that the HEATER inside the sensor does not work, which causes the sensor to work slowly while cold -- the period after initial engine start.

Diagnosis of the heater requires a simple test -- open or short -- using an ohm meter.

There are four wires to the sensor, two for the heater part and two for the sensor part. While the sensor itself might be working fine, the heater failure requires the sensor to be replaced. It is not possible to repair/replace the heater without replacing the sensor, except that the heater could fail as a result of a broken wire somewhere in the car. The ohm meter on the heater leads of the sensor will tell you if the wires are the problem. I'd expect an ohm (continutity) test to expose an open circuit, not a shorted one. If the heater is open OR shorted, then the wires should be okay, if the heateter is okay, then the wires are open or shorted.

Reply to
Jeff Strickland

Thank you for your reply.

What do you mean when you say to check to if the throttle position sensor has been disturbed?

Is there an adjustment for it? If it was faulty, would there be a code associated with it?

Reply to
Lawrence Woodruff

Thank you for your reply.

What do you mean when you say to check to if the throttle position sensor has been disturbed?

Is there an adjustment for it? If it was faulty, would there be a code associated with it?

************** You're welcome!

If the throttle position sensor has been disturbed, then you would likely see marks on the screws that hold the sensor in place. If the sensor is faulty, then you would see a trouble code, but if it is not adjusted properly, you would not necessarily see a code.

Reply to
Ray O

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