SlowRider1

I have 99 ES300 with VSC, VSC OFF, and CHECK ENGINE lighs on.
Mechanic pulled some codes
PO125 = Coolant Temp Sensor (29.99 and autozone)
P1135 = Air/Fuel Ratio Sensor Bank 1 Sensor 1


So i got the coolant temp sensor and now i am trying to buy the O2 sensor, or is it the Air/Fuel Ratio sensor. Another post on this forum described the replacement of o2 sensor in 1997 ES300. There, the guy used O2 sensor.

I checked ebay and found O2 sensor for $40 and Air/Fuel sensor for $130
which one am i supposed to buy? or maybe i should go to the dealer?

EDIT: thank you all for posting much useful info!!!!

GEORGE_JET

P1135 is for the O2 sensor heater circuit. On these years you have 4 wire O2 sensors, 2 of the wires (generally the white wires) are for the internal heater. Before you spend money on a new O2 sensor it would be a good idea to ohm out the heater. If that is good check the connectors. Bank 1 Sensor 2 shares common circuit all the way up to one splice just before the sensor, since you are not getting a error for this sensor also, the chances of a bad fuse are slim. You could also try reseating the ecm connector ( the ecm supplies the ground to each individual sensor) Good luck

JSM1284

CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way catalytic converter is used, but for the most efficient use of the three-way catalytic converter, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio.
The A/F sensor has the characteristic that provides output voltage* approximately proportional to the existing air-fuel ratio. The A/F sensor output voltage is used to provide feedback for the ECM to control the air-fuel ratio.
By the A/F sensor output, the ECM can determine the deviation amount from the stoichiometric air-fuel ratio and control the proper injection time immediately. If the A/F sensor is malfunctioning, ECM is unable to perform accurate air-fuel ratio control.
The A/F sensor is equipped with a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temp. of the exhaust gas is low), current flows to the heater to heat the sensor for accurate oxygen concentration detection.
*: The voltage value changes at the inside of the ECM only.








INSPECTION PROCEDURE

HINT: Read freeze frame data using LEXUS hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected, when troubleshooting it is useful for determining whether the vehicle was running or stopped, the engine warmed up or not, the air-fuel ratio lean or rich, etc. at the time of the malfunction.

JSM1284

P0125




Insufficient coolant temp. for closed loop fuel control

CIRCUIT DESCRIPTION




To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way catalytic converter is used, but for the most efficient use of the three-way catalytic converter, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio.
The A/F sensor has the characteristic that provides output voltage* approximately proportional to the existing air-fuel ratio. The A/F sensor output voltage is used to provide feedback for the ECM to control the air-fuel ratio.
By the A/F sensor output, the ECM can determine the deviation amount from the stoichiometric air-fuel ratio and control the proper injection time immediately. If the A/F sensor is malfunctioning, ECM is unable to perform accurate air-fuel ratio control.
The A/F sensor is equipped with a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temp. of the exhaust gas is low), current flows to the heater to heat the sensor for accurate oxygen concentration detection.
*: The voltage value changes at the inside of the ECM only.

DETECTING CONDITIONS



HINT:


After confirming DTC P0125, use the OBD II scan tool or LEXUS hand-held tester to confirm voltage output of A/F sensor from "CURRENT DATA'.
The ECM controls the voltage of AFR+, AFL+, AFR- and AFL- terminals of ECM to the fixed voltage. Therefore, it is impossible to confirm the A/F sensor output voltage without OBD II scan tool or LEXUS hand-held tester.
OBD II scan tool (excluding LEXUS hand-held tester) displays the one fifth of the A/F sensor output voltage which is displayed on the LEXUS hand-held tester.
WIRING DIAGRAM



INSPECTION PROCEDURE

HINT: Read freeze frame data using LEXUS hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected, when troubleshooting it is useful for determining whether the vehicle was running or stopped, the engine warmed up or not, the air-fuel ratio lean or rich, etc. at the time of the malfunction.

JSM1284

SlowRider1

I do have ground problem. My dash clock is dim, I can barely see the time. When I rev up the engine it gets brighter. Headlights and the dome lights are flickering when the engine is running.
Initially i thought it was faulty alternator, but I replaced it 6months ago and the problem with dim/flickering light never went away.
I've checked my ground cable from battery to chassis, it seemed ok.
any other suggestions?

SlowRider1

so I got the coolant temp sensor, and while i was in autozone i checked the codes again. 2 new codes poped out:
P1130:
Lexus: Air/Fuel ratio sensor circuit Range/Perfomance malfunction (bank 1 sensor1)
Probable causes: 1. Fuel Pump, injector or pressure regulator fault
2. Vacuum Leak on engine
3. Faulty AF Sensor heater circuit
4. Failed AF Sensor
Toyota: Air/Fuel sensor circuit Range/Performance (bank 1 sensor 1)
Probable causes: 1.Open or short circuit condition
2. Poor electrical connection

P1133:
Lexus: Air/Fuel ratio sensor circuit response malfuntion (bank 1 sensor 1)
Toyota: Air/Fuel sensor circuit response (bank 1 sensor 1)
Probable causes are same as those for P1130.

so its the circuitry?

Today, I am planning to check my voltage on ECM as was pointed out above.

SlowRider1

i just took readings
HAFL(+) TO GROUND = 12.24V
HAFR(+) TO GROUND = 2.37V

could this be caused by poor connectivity?

SlowRider1

i just did further research. the following is a diagram for 2001 ES300
according to this O2 Sensor Bank 1 Sensor 1 is by the firewll.
In 1997 ES300 however, Bank 1 Sensor 1 is located by the radiator (see my next post). I have 1999, my Bank 1 Sensor 1 is by the radiator right?

SlowRider1

1997 ES300 O2 sensor locations

lexway07

So is the location of A/F sensor at bank 1 sensor 1 on 1997 model picture above same as on 1999 model ?. I have a same 1999 es300 and getting P1135 with bank 1 sensor 1 .i need to replace A/F sensor at bank1 sensor but want to make sure of the location for 1999 model.. Please help!!!

SlowRider1

the A/F ratio sensors of 99 ES300 are same as those pictured in the diagram from 2001. I finally fixed mine, drives nice.

WSU LEXUS

as the dtc said a/f sesnor is most likley a air fuel sensor not a O2 sensor
also if you look on the sensor if its an oem senor you look at the part number on it
some thing like this 894xx-41030 not exatly
but if the xx=67 it is an air fuel sensor if xx=65 it is a O2 sensor

delta901

I have a 01 with P1135. Checking endlessly to find part #. Please let me know what is the part # you replaced and where to order it.

Thanks!

delta.

EScrow

Part # for Bank 1 Sensor 1 is 89467-41030. Best price I've found is here: http://cgi.ebay.com/ebaymotors/GENUI...spagenameZWD1V. It's $139.00 free shipping.

If link doesn't work, do a search in ebay with that part # and be sure to click the "search title and description" box.