hi guys,

my car is 99 es300, 74k miles, changed timing belt and 2 cam seals and crank seal. now i'm getting check lights, so OBD 2 to checked the code, p1135 and p1155. i changed both sensors front and back (Denso, original parts), cleaned MAF, replaced air filter (K&N). unplug battery and plug back on, and still getting cel light. I checked see if bad fuse and relay, they are fine. what else can i do to get rid of dam lights. please help,,,,,

Does anyone had same experience?

If you clear the codes and reset the ECU, do they come back insantly when you drive the next time? If so, this would indicate a "hard" fault and something is wrong w/ the sensor you replaced. If you drive the car and it takes a while for the CEL to come on and you check the codes, does it show a "pending" code? If it's a pending code, then the sensor is fine but something else is causing the issue.

Did you replace the sensors because you were getting codes before? Did someone say you needed to change them? I didn't have to change my Air/Fuel sensors until 230k miles.......

When it comes to the Air/Fuel sensor or 02 sensor, I use Toyota OEM parts, nothing from Autozone, etc.......

how do you know the A/F relay is working? I'm pretty sure that's the culprit. It controls both of the heater circuit on the A/F sensors on both banks.

when i start the car no cel, when I turn off ignition and start again about min later it comes on. I'm getting p1135, p1155, p1135, p1155 on my obd 2. what is pending code? I did search and that is why i changed 2 sensors. yes, i did use toyota oem parts because what i read in this forum.

From your description, the codes that are being triggered are NOT "hard" faults......it takes one ignition cycle for a "hard" fault - light would come on instantly. A pending code is the ECU "sees" a potential problem but "waits" to see if the condition remains again on the next ignition cycle. If it does, then it triggers the CEL.

You said you changed your timing belt - are you 100% positive you aligned ALL the marks correctly when installing the new t-belt? My hunch is that it is off a coupe of teeth and the ECU can't compensate all the way changing the air/fuel mixture - thus throwing both codes for both sensors at the same time........

Go check this and let us know your findings.........

when i checked fuse it was fine but relay, i'm not sure, i just guess it's ok, because when i read this forum someone said if you have 4 different codes then it's bad relay, but mines are 2 codes and repeating (p1135, p1155, p1135, p1155)... if it's relay, do you know which one it is? i want to check it.
thank you

yes, the timing belt marks are right on. acutely, p1135 came on first with p0171. so when i checked air hoses it was 2 hoses were cracked so i replaced it, then code p0171 is gone. i'm guessing about 20 miles later after p1135, p1155 came on.

The A/F relay is under the hood I believe. It's labeled as "A/F RELAY". To test the relay, disconnect the relay. Flip the relay over. Look for pin 30 & 87. Get a DVOM, set it to continuity check, touch the pins, it should have continuity. Pins 85 & 86, get a jumper cables apply battery power and ground to it and hear it click, if doesn't relay no good. Make sure the A/F fuse is good also.

i switched horn relay and a/f relay(same part number), but the relay seems fine(horn works). the cel light still there.

Clear the engine light. And see if it comes back. If it does, you got a wire integrity problem

I checked relay and it's fine. clear the cel, but still having the cel.

Most likely the heater elements of your two new A/F sensors are no good (in spite of being new).

If fuse, relay, wire integrity, and both A/F ratio sensor is good, the only thing left is the PCM but i doubt it. If you are not good with electrical, time to give it to the mechanics. Only thing i can think of is a wire integrity issue. GL