stirfryboy

So trying to get my 01' ES300 to pass smog. Won't pass. Here is what is happening: I drive to set the monitors and all the monitors except catalyst are set. No CEL. The tester connects their computer and lo and behold P0135 and P0155 pop up. I reset the computer, and try again to see if it's a coincidence. Nope, 3 times they connect their tester and 3 times those codes come back. I can drive 300-500 miles and not have the CEL come on. Any ideas?

Just replaced the front AF sensor with a Denso (not original sensor, not Denso) and pulled the rear sensor. Rear sensor has no labels on it, no manufacturer name at all. New Denso sensor coming later this week.

Any input or advice would be greatly appreciated.

nsghtbrwry

Hm, codes are for front bank sensor. I'm guessing some weird electrical problem, I'd start by cleaning all the grounds under the hood (think there's one right on the bracket where the O2 sensor connector mounts).

When you get the new sensor in, I'd put that in the front and move the older, still-new sensor to the rear bank. That way you can see if the code moves. Won't matter because the Denso offering for these cars is the same for front vs rear bank.

When you drive around to get the monitors to run, here are the instructions to get them to run without random driving: http://www.totalcardiagnostics.com/s...i-drive-cycles

...either they will run, or codes will set (since you mentioned the catalyst monitor didn't run).

stirfryboy

replaced the front sensor with a Denso. Rear sensor is brand new, but not a Denso. Then the codes came on again once the state's computer is connected. Thanks for the link. Any more ideas to get this thing to pass smog?

Ground connections look good, this car was from Vegas. No rust or corrosion.

stirfryboy

Update: if I leave my OBD reader unplugged from the car, the CEL illuminates with codes P1135 and P1155. So now it's independent of testing for SMOG

nsghtbrwry

I'd still swap your new rear sensor with the front Denso. If the codes move to the rear, bad Denso sensor. If not, wiring problem or busted ECU.

stirfryboy

Spent 2 hours going over the wires tonight, checking all the ground wires and cleaning them with brake cleaner. No rust, no corrosion. All are in the correct place and clean. Ordered another AF sensor for the rear, I pulled it and no markings on it as far as what brand it was. It is new, definitely aftermarket. So now I'm down to the ECM or the rear sensor causing the issue.

Also replaced the AF heater fuse for good measure, swapped out the AF Heater relay for the Horn (same part number), and the horn worked. So I know I have a good fuse and relay.

stirfryboy

Finally got to replacing the rear upstream AF sensor. CEL came right back on. Bummer.

I've cleaned the MAF

Any ideas before I break down and take this thing to the stealership?

nsghtbrwry

Maybe the wiring from the sensor(s) to the ECU are bad?

stirfryboy

Took it to the stealer today. Diagnosis is no ground from EFI circuit. I don't know where that ground is. Don't know how that happened. Anyway it was $115 to fix and then I had them do an alignment. So around $220 for everything. ECM should be fine.