2003 sienna check engine light

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calvinnnnnnnnn

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well i did an oil change for my dad's car and like 4 days later the check engine light went off. Is this a coincidence?

going to run the code tomorrow....but would like some inputs first.
 
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sienna. did you leave the gas cap loose or fill up the tank too much. The famous al gore emissions light.check emmissions hoses and canister plus valve if those aren't it. po440 if i remember right.
 
I had that code on a '97 Honda Civic Del Sol. Replaced the O2 sensor because the heater had gone open-circuit. I tested it with a multimeter first. That was the first time I'd ever seen that particular problem with an O2 sensor.

As I recall it was a Denso sensor. Hopefully they don't have problems with heater failures, because I replaced the ones in my Crown Vic with Denso sensors and that job is something I don't care to have to do again anytime soon.
 
2003 Toyota Sienna, 1MZ-FE motor.
Bank 1 is the rear bank of cylinders.
You can see the bank 2 sensor 1 on the front.....the bank 1 sensor on the rear will be similarly located.

The heater resistance as measured from the B+ pin to the HT pin on the sensor should be 0.8 to 1.4 ohms at 68 degrees F.
You are measuring between pins 1 and 2 on the oxygen sensor.

This information is from the 2003 Toyota Sienna service manuals.

NOTE......zero out your ohms measurement......you can do this by connecting the meter leads together.......whatever resistance you read......subtract that value from what you measure.
In other words....you measure 0.4 ohms when you connect your meter leads together.......and 12 ohms when you measure the heater in the sensor.......12-4 gives you 0.8 ohms for the sensor heater resistance.

I notice that Toyota calls the sensors before the catalytic converters "Air-Fuel ratio sensors" although they are oxygen sensors....and the 1 post catalytic converter sensor "heated oxygen sensor".
 
I had the heater go out on a Denso O2 sensor on my 2002 Isuzu Rodeo (4 O2 sensor system). It doesn't effect the functionality of the sensor aside from a slower warm-up time. Bad thing is- You'll have a constant CEL until you replace it. I'd price a replacement online. I know my Isuzu dealer wanted something ridiculous like $240 for this O2 sensor, but I was able to source an OEM online for ~$100. Prior to replacing with the OEM Denso, I tried a supposed exact fit Bosch and a Walker. No go. The connectors were different. If it was an older vehicle at the time, I would have spliced it, but it was only 3yrs old.

Joel
 
AlldataDIY shows the list price to be $212.83
I checked several online dealershp parts departments, and they don't list the rear one.....but list the front one.
I looked at Rockauto, and they list the 8946741030 for the front, Denso number 2349021.
When I look the 8946741040 number up on the denso website, they list the denso #2349021 for the rear.....which is the same part as is called out for the front.
Denso states that it is a "first time fit", direct plug in, no wire cutting.
The front one has leads that are just over 13 inches, and the rear one that Rockauto lists has just over 11 inch leads.

So.....if it were me, I would buy the Denso 2349021.
The Denso Website lists it for $152.10 (on sale)
The Rockauto Website lists it for $136.79
Toyotaparts123 lists it for $96.40
Toyotapartscheap lists it for $107.81

Of course, check out the shipping charges.

Anyhow, I am a stickler for wanting to have the front and rear bank oxygen sensors a closely matched as possible......same switching charactoristics.....so that you have a ballanced situation between the 2 banks of cylinders.
The only difference between the OEM DENSO oxygen sensors seems to be about 2 inches in lead length......and the front one is the one with the longer leads......so I see no reason that it would not be a good choice for the rear bank.

That is.......if the sensor is indead defective.
If the heater circuit does check out.....then the connections to it will need to be verified.

The B+ for both the front and rear oxygen sensor (pin2) goes throught the A/F Heater relay (remember that TOYOTA calls them A/F sensors)through the 25 Amp A/F Heater fuse, to the battery.

The A/F Heater relay is energized from ECM pin 8 "MREL"
This same ECM pin also energizes the EFI Relay.....which also provides power to the fuel pump.....

If the front oxygen sensor heater is working.....I am going to say that power is coming from the fuse and relay.....if not....post back.

So, if you have B+ to the front sensor, and not to the rear sensor.....verify the connector......etc.

The other lead at pin 1 of the oxygen sensor goes......Bank 1 (Rear sensor) to the ECM pin 3 "HAFR".
Pin 1 of Bank 2 (Front) sensor goes to ECM pin 4 "HAFL"

Pins 3 and 4 are the + and - sense leads.
Bank 1 (Rear) Pin 3 connects to ECM pin 11 "AFR+"
Bank 1 (Rear) Pin 4 connects to ECM pin 20 "AFR-"
Bank 2 (Front) Pin 3 Connects to ECM pin 12 "AFL+"
Bank 2 (Front) Pin 3 Connects to ECM pin 21 "AFL-"
 
One point that I was trying to make.
The online TOYOTA parts departments that I looked at did not list anything for the Bank 1 sensor (rear one).
So I dug deeper and found that the Bank 2 sensor has the SAME plug (as per DENSO), and leads that are about 2 inches longer.
So....I recommend that you purchase the sensor listed for BANK 2 (FRONT) for the bank 1 (rear) as this is what DENSO recommends.
Rockauto lists a different number for the bank 1, I don't know if it is identical or not......so I would stick with DENSO's recommendation.

Toyotaparts123 looks cheaper, but you would want to verify any difference in shipping charges.
 
I don't know about Toyota, but on my Crown Vic, the sensors for the upstream and downstream use different keying on the connectors, but the actual sensor itself is the same.

Denso's solution to this, so they could use the same part number for both applications, is to use a connector that has no keys on it, so it will plug into either the upstream or downstream connector.
 
The link took me to the home page for the site.
When I drilled down.....they call them oxygen sensors on that site.......they have "front" and "rear".
The one for the rear bank is the one that you need......which they don't have a listing for.
HOWEVER, the one in the front bank is the exact same part......with leads that are about 2 inches longer.......
So.....use the one for the FRONT.

8946741040 is, I believe, a TOYOTA part number......which crosses to a DENSO number. Same exact part.......just a OEM number and a manufacture's number.

8946741030 is the exact same part.....except that the leads are about 2 inches shorter....
It looks like they use the 1 part in the replacement market.

HOWEVER, if you want to ask the dealership......there should be a link to ask them a question.
It is best to include your VIN with parts orders through a dealership.
I do not think there was any mid-year change for the oxygen sensors......but that could be the case for some other parts.....and they can put your VIN into their computer when processing your order.....making sure that they are selecting the correct part for your particular vehicle.

You have 3 oxygen sensors......
1 on the front (bank 2) just below the exhaust manifold.
1 on the back (bank 2) similarly located as the front on.....but in the back.
These are used for control of the motor.....Air/Fuel mixture being the major one.......how much fuel to spray into the cylinders to mix with the air that is going in.
These are often called "upstream" oxygen sensors as they are located before the catalytic converters.

The 3rd sensor is located AFTER the catalytic converter that is under the vehicle.
This is a DIFFERENT sensor from the other 2 sensors that we have been talking about in this thread (I see a different resistance value for the heater circuit).
The ONLY function of this sensor is to verify that the catalytic converters are working.
 
i called the toyota dealership and they gave me this part number:
8946509290
this is what i get:
Screenshot2010-02-17atWed2172010820.png


here is the part number you gave me 8946741030
Screenshot2010-02-17atWed2172010818.png


im not sure which sensor is right? denso or what toyota sent me? they might have given me the wrong number....

what is the difficulty in installing this sensor?
 
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There may be confusion in terms of sensor naming. Generally, the naming for sensors is with cylinder bank number (1 or 2) and front (before Cat Converter) or rear (after Cat Converter).

Toyota uses the expensive air-flow ratio (also called wide-band) for the front sensors which are used to calculate the mixture and are critical for the engine operation. The rear sensors are only used to monitor the performance of catalytic converter efficiency and are instrumental in triggering P0420 or P0430 when you converter is no longer operating at its 100% efficiency.

- Vikas
 
I wonder if you can get lucky and be able to read the numbers on the oxygen sensor that is in the front?

I will gues that both sensors will work......and that they are both DENSO brand.

I have not changed the oxygen sensor(s) on my 2003.
The rear one (bank 1) is going to be harder....due to the location.
The new sensor may have some anti-seize paste on the threads.

Make SURE to route the wires so that they are not touching any HOT exhaust parts......etc.....or any sharp edges.
 
When I go to that site, and drill down using my vehicle year/model......I get the $96.40 part.
So, that is what I would buy.

You could also try toyotapartszone and search by entering your VIN

That site also has some nice diagrams.
 
so the o2 sensor is seized,,...

any ideas how it get it off without stripping the threads? the toyota tech said there is a 50/50 chance we have to buy a new exhaust manifold..
 
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