Tmmoll

Hello, I am new to the Lexus world and just picked up a 2007 GX470 with 125,000 miles. I bought it knowing it had the P2240 code and thought maybe the o2 sensor was bad. I bought an oem Denso o2 sensor and replaced it. Cleared the code, then took it for a test drive. Code came back less then a mile later.



Took it to a shop so they could hook it up to there computer and found that power is going to the o2 sensor, but nothing is going back to the ecu.

Would this be a sign that the ecu needs repair? Or maybe a wire is bad for the signal to go back to the ecu? The o2 sensor I pulled was also a Denso oem.

Where can I find the wires that go from the o2 sensors to the ecu?

Lexus4321

Nothing going back to ECU?
If a signal goes from O2 to ECU, then how is the ECU the issue?

It's just the passenger side front sensor? What sensor exactly did you install?

Tmmoll

The shop put it as no data is going back to the ecu. When the throttle is activated, nothing changed on their scanner, but it is showing as active voltage.

part that was replaced was bank 2 sensor 1 (upstream passenger side) with Denso 234-9051.

The thought I had for a bad ecu was something is damaged not allowing the signal to be received, I.e. damaged pin, short in the ecu, something like that.

chiph9

I would first check the connector on the sensor that was replaced for loose pins, etc. And check the wires from the sensor to the body harness for damage (perhaps a rodent chewed on it)

Chip H.

Tmmoll

can you please advise me on the routing for the harness? I’m new the the Lexus platform coming from a duramax so I’m not familiar with the Lexus wiring.

chiph9

Just follow the 1-2 feet of exposed wire from the sensor to the main harness, as that's the most likely place for damage.

Chip H.

Tmmoll

Does the harness go into the body through the center console? I see where it goes over the bell housing, but I can’t see anything past that or get my hands in there.

Is there a way to test the the main harness connector (not the o2 sensor side connector) to see if there is a short? What pin/wire color is for the data to go back to the ecu?

chiph9

I've not been up in that area. But I believe it will head towards the firewall and join other wiring there.

If you want to check at the ECU (behind the glove box/passenger kick-panel), this is the info I have for my 2004. Yours may be different - Toyota makes mid-year changes to vehicles.

B-22 | Bank 2 Sensor 1 | Green | Oxygen reading
B-33 | Bank 2 Sensor 1 | Black-Blue | Heater control
B-23 | Bank 1 Sensor 1 | Red | Oxygen reading
B-4 | Bank 1 Sensor 1 | Light Green | Heater control
B-21 | Bank 2 Sensor 2 | White | Oxygen reading
B-25 | Bank 2 Sensor 2 | Pink | Heater control
B-29 | Bank 1 Sensor 2 | Black | Oxygen reading
B-5 | Bank 1 Sensor 2 | Green-Yellow | Heater control

These are the connector, pin, which bank+sensor, wire color, and purpose
Unfortunately I couldn't determine which connector is "B" on the ECU but looking for the colors in pin order should work.

The 12v for the sensors do not go to the ECU but to junction connector J26 which is to the left of the ECU, more behind the radio. Look for multiple Blue-White wires (+12v) opposite multiple Brown wires.

Chip H.

Tmmoll

Thanks a bunch. I had to take it back to the shop. I live in an emissions area and need it fixed fast. I’ll pass this info on to them if they can’t figure anything out.

Tmmoll

So just got a call from the shop. Apparently there is a short somewhere in the wire harness under the engine. They took the air intake off and saw a lot of crap work, loose and damaged connectors, and pinched wires from zip ties being too tight. They want to install a new harness, but that is way outside my budget if they for it. Anyone have Experience in replacing the engine harness? How difficult is it? Is this something I can tackle myself? I know the intake will have to come off as well as the timing cover.

chiph9

eBay or a parts yard will likely be your best bet. The online parts catalogs show an "engine harness" as the only available one.
And it's really the engine compartment harness (not actually on the engine - it runs the headlights, etc.) MSRP on that is $4k

See if you can get a part number from your dealer. That will help in your searches.
Otherwise you're probably looking at repairing the existing harness from what was likely rodent damage.

Chip H.

Tmmoll

I found this one. Part Number: 821216A504


It’s $1400 from a Lexus dealership. I am ok with getting a new harness instead of junk yard or eBay. This way I know all the connectors will be new.


repair shop said pt number is 821116a433but I can’t find any pics of that harness.

chiph9

Use your VIN to make sure you get the right one. Like I said - Toyota makes running changes to their vehicles.

Chip H.