Help 1999 Sienna Getting 10 mpg! - Toyota Nation Forum : Toyota Car and Truck Forums

Yesman · 08-05-2011, 09:06 AM

I am now the proud owner of a badly neglected 1999 Sienna, and now am trying to fix all the problems. The CEL is on and used the scan tool at Advanced Auto. I got the following:

P0171 -Bank 1 System too lean

P1130 - Air /Fuel Sensor Circuit Bank 1 Sensor 1

P1135 - Air/Fuel Sensor Heater Malfunction Bank 1 Sensor 1

So my assumption is I need to change the A/F sensor, right? I have a Haynes manual and very little experience, but the manual does not seem clear as to where the sensor is or how many there may be. I hope to get under the vehicle this weekend, and sure would appreciate any thoughts about this.

Really like this site and have found a lot of good information already. Thanks to all who contribute!

Black Sunshine · 08-06-2011, 06:35 PM

Bank 1 Sensor 1 is also known as the fun one. It's just below the exhaust manifold on the back of the engine. It's a tight squeeze but it can be changed by reaching up from underneath. Plugging the sensor back in is harder than changing it.

SiennaDriver · 08-06-2011, 07:53 PM

Sounds like you need that dastardly firewall sensor and something's amiss around the MAF sensor. That's the thing that's mounted on the air cleaner housing.

You didn't post mileage or how neglected maintenance has been. Maybe it JUST needs recommended periodical service, tune up etc?

Yesman · 08-07-2011, 06:59 AM

Thanks Black Sunshine. Sounds like fun. I have got to do the rear brakes this morning, so I will take a look at it while doing that. May get some time later in the week to do the sensor.

Yesman · 08-07-2011, 07:03 AM

Thanks SiennaDriver. I just got the van, but it looks like the previous owner did as little as possible. It has 122,000 miles, and probably needs a tuneup, as suggested. Is there any way to determine if the MAF is working properly? Thanks again.

SiennaDriver · 08-07-2011, 10:42 AM

Quote:

Originally Posted by Yesman

Thanks SiennaDriver. I just got the van, but it looks like the previous owner did as little as possible. It has 122,000 miles, and probably needs a tuneup, as suggested. Is there any way to determine if the MAF is working properly? Thanks again.

Yes, you should get resistance readings from the various terminals within specifications posted.

A diagram and instructions can be had if you search for the link to the service manual that's somewhere else on this site. It's also elsewhere online or maybe in your service manual.

That's really bad mileage.