Replaced Bank 1 sensor 1 O2 heater but CEL still on. (1 Viewer)

[BLC]

Hi all,
Backstory: I recently purchased a 2000 with ~200k mileage here in New England. Windshield leaks (getting replaced this week, bad install), CEL on and throwing P0135 (Bank 1 Sensor 1 O2) But other than that, minimal rust on frame and beautiful body (was garaged most it's life)

I mistakenly replaced the O2 sensor with a Denso 432-4169 before checking the original. After checking both, the replacement and original with a multimeter, they're both operating correctly (iirc returning 16ohm). I replaced anyway, cleared the signal and ran the truck for ~10 miles on the highway and the CEL came back.

I have checked the O2 sensor wire harness with the key in the "on" position and one black wire returns 12V and the other black wire returns a junk measurement. (Is one power and the other ground?)

I have checked the ECU via the 2004 FSM floating around, but it seems the 2004 ECU is different from 98-2001, so I'm not sure if I was testing the correct ports. I tested the wiring harness that plugs into the ECU but the wire that is supposedly Bank 1 Sensor 1 isn't returning any voltage, but the wire that is supposedly bank 2 sensor 1 is returning ~7v.

So it sounds like the wire is shorting somewhere. Before I go and replace the wire (soldering in that small real estate of wiring from the Bank 1 Sensor harness is going to be a PITA) is there anything else I can do/check?

 

[Spike555]

Vacuum leaks, check for vacuum leaks. Enough unmetered air can set off O2 codes, I have heard of intake gasket leaks causing this but no personal experience.
Also large exhaust leaks can set off O2 codes.

 

[Poncherelli]

Did you buy this cruiser in Massachusetts?

 

[BLC]

Vacuum leaks, check for vacuum leaks. Enough unmetered air can set off O2 codes, I have heard of intake gasket leaks causing this but no personal experience.
Also large exhaust leaks can set off O2 codes.

Thanks, I'll check for vacuum leaks, I'll also smoke the exhaust, although did a quick audio/visual check and nothing out of the ordinary. PO said they replaced exhaust manifolds. Might check there first.

 

[BLC]

Did you buy this cruiser in Massachusetts?

Yeah, last week, you know it?

 

[morganism]

The "Readiness monitor drive pattern" needs to be reset correctly. There is link in the faq. After restarting, set idle, after fan comes on, then set brake idle w foot on brake, and truck in Drive.

If it's an 01, u can prob run it wout either O2 if up don't mind havn the CEL on all the time. I have been running the folks Corolla for 2 years now w 02 unhooked, w nearly same mileage. There is a firmware bug in the ECU, that triggers every time coolant temp, and exterior air temp is 45 deg diff at start. Happens often in desert.


Edit, Readiness was in the 80 fan

• TSB_EG003-02_(revised) 96-02 readiness monitor drive patterns.pdf
  File size:
  138.2 KB

 

[white_lx]

Wiring diagrams can be downloaded for free from bbbind.com. The diagram for your cruiser is attached. See page 2 for the Bank 1/2 Sensor 1 wiring.

The ~7V is your DVM measuring the average voltage to the sensor that is working. The heater circuit is a 12V pulse width modulated circuit. If you don't see the same kind of number at your faulty sensor (or higher), then the wiring is certainly suspect.

Are you able to measure the resistance through the sensor at the CPU connector? Also check the pins of the connector. There could be some corrosion.

 

[BLC]

Edit, Readiness was in the 80 fan

• TSB_EG003-02_(revised) 96-02 readiness monitor drive patterns.pdf
  File size:
  138.2 KB

Thanks for this. I'll clear the code again and try this.

 

[BLC]

Are you able to measure the resistance through the sensor at the CPU connector?

I'm sourcing some longer leads for the multimeter to test the resistance from the harness to the ECU connector, that was my final step before replacing the wire.

Also, thanks for the 2000 wiring diagram

 

[white_lx]

You can also check if you have 12V at the B-Y (black-yellow) wire at the connector.

 

[Poncherelli]

Yeah, last week, you know it?

I saw it for sale. Looked like a nice unit, but I had just bought mine a few months prior so never pursued. Where you located? I’d love to get together and check it out...just for kicks...not too old at diagnostic.

Looks like you’re running electrical checks, but I had a similar code and ended up being leak related.

Yeah, last week, you know it?

 

[Spike555]

The "Readiness monitor drive pattern" needs to be reset correctly. There is link in the faq. After restarting, set idle, after fan comes on, then set brake idle w foot on brake, and truck in Drive.

If it's an 01, u can prob run it wout either O2 if up don't mind havn the CEL on all the time. I have been running the folks Corolla for 2 years now w 02 unhooked, w nearly same mileage. There is a firmware bug in the ECU, that triggers every time coolant temp, and exterior air temp is 45 deg diff at start. Happens often in desert.


Edit, Readiness was in the 80 fan

• TSB_EG003-02_(revised) 96-02 readiness monitor drive patterns.pdf
  File size:
  138.2 KB

Can you explain more this firmware bug about temps? What years does this affect? Is there is fix?

 

[BLC]

Update. Windshield has been replaced. CEL was still throwing code for o2. Couldn't find the issue so I left it as is and ran it for a couple weeks. That is until last Saturday when I was planning on taking it on a trip and it broke down.

Everything just shut off on the highway. I pulled over and tried to start it. It turned over but didn't start. I figured it was either the timing belt or a fuel pump issue.

Towed it home and popped the timing belt cover off and turned it over and the belt moved. Thankfully.

I removed the fuse box and found that the efi fuse had been blown. I replaced it with a new 20a fuse and tried again. As soon as I try to turn the car over the fuse pops. (I noticed that the immobilizer light is on, but this may be a red herring. Read below)

I bought a 2 day sub to TIS and spent hours manually downloading the repair manual and EWD. (I may come up with a new solution for bulk downloading , but that's another day.)

I have tested the heater resistance between the bank 1 sensor 1 o2 sensor and pin 4 of the e6 connector on the ECU and it was reading under 1ohm so I'm assuming no short there. I tried testing the other connector from the o2 to pin 12 on the ECU but that was reading open.

Am I correct in assuming the heater pin (4 on the ECU harness) just gets the pulse signal to turn off the heater and the other pin (12 on the ECU harness) that is shorting, is the voltage signal? I will post a diagram shortly.

 

[2001LC]

You may want to consider one or more:

1. Water entry. Very common with bad windshield install. Water runs down "A" pillar into wining and electronics into side panels and under dash. Typically the issue clears after drying out, but short can permanently damage ECM. Also if leak was longer term, some permanent damage may have accrued.
2. Fuse box corrosion/short.
3. Rodent damage.

Never hurts to get a second set of eye on the problem. Consider taking to Toyota Dealer and have them take a look.

 

[BLC]

Update: the problem has been fixed. I traced the short in the circuit from the fuse box back to E4 splice point then disconnected the IN1 connector and the short went away. So that led me to the circuit from the o2 sensor to the E4 splice.

I went to unraveling the mess of wires at E4, in hindsight, after getting the fault from the ECM, I should've started at sensor. But after not finding anything at E4 I decided to skip E10 and go right to the o2 sensor.

I tried to get to the o2 connector but the heat shield was in the way. I removed the heat shield and wouldn't you know it, the short disappeared. So I jacked the truck up and removed the plastic cowl in the wheel well to get a better view of the connector and it looks like the PO had hammered the heat shield into the wiring above the connector.

I applied silicone to the exposed wiring, bent the heat shield back outward, installed a new battery (it needed one anyway) and it started right up.

Thank you all for the help and suggestions.