posted 06-29-2005 03:12 PM               

I have a 1999 Toyota 3.4L V6 SR5 4WD (manual transmission) with California Emissions. 2 years ago, my "Check Engine" light came on. I've been ignoring it for a long time (almost 40,000 miles!) but now I need to get my Mass. Inspection sticker, so I need to fix it. My vehicle now has 140,000 miles, and I've never replaced any Oxygen sensors (I guess it's also called a fuel/air ratio sensor on vehicles set up for California emissions, like mine).

Going to an "Autozone" auto parts store, they hooked up the diagnostic connector on my 4Runner to their OBD II handheld diagnostic device. The device indicates the error codes were 1135 and 0125. Inside the store, they can look up the codes on their computer. Assuming you always add a P to the code, they are:

P1135: "Pedal position sensor A circuit intermittent".
P0125: "Insufficient coolant temperature for closed loop fuel control".

Let’s start with the first one: P1135.
Huh??? I have heard of a "Throttle position sensor", which is located under the hood on the throttle body, and detects the throttle position. Does anyone know if the "Pedal position sensor A" is the same thing as the “Throttle position sensor”? I want to be sure. I looked on the OBDII home page, and I could not find error code P1135 listed! Since the first “1” in 1135 indicates “manufacturer”, and a “0” in that position indicates “SAE (Society of Auto Engineers)”, I’m thinking that 1135 is a special code specific to Toyota and not the general OBDII codes for all vehicles. The closest OBDII code I found was:

P0124 Throttle/Petal Position Sensor/Switch A Circuit Intermittent

So, I’m not sure what P1135 really means, since P0124 has the same meaning according to the ODBII diagnostic code table.

If I assume the description of 1135 on the computer at Autozone was inaccurate, and I try to match 1135 with the ODBII diagnostic code table, the closest match is P0135, which is:

P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

Though, I had the codes checked a month ago (after neglecting them for 2 years), and the code P0120 was stored, along with 1133, 1135, and P0125. P0120 is:

P0120 Throttle/Petal Position Sensor/Switch A Circuit Malfunction

So, does anyone know if I have a real problem with my Throttle Position Sensor (“TPS”)? Or, does is there really a problem with the O2 Sensor Heater Circuit (assuming the code P0135 is what I should go by)? I was thinking that because of the next code P0125.

Another confusing thing. For code P0125, The computer at Autozone, as well as the IDBII Diagnostic code table, has this:

P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control

My coolant temperature has been fine, and the level is fine. However, when I looked in a service manual (by “Haynes”), that same code is listed like this:

P0125 O2 Sensor heater circuit fault.

Wow – could this be my pre-catalytic converter Oxygen Sensor failing? What’s up with the strange description “Insufficient Coolant Temerature for Closed Loop Fuel Control”?

Anyway, if anyone has any experience with these error codes, I’d appreciate the help. Also, if it does turn out to be the O2 Sensor, what are the odds I’ve ruined my catalytic converters? I have two, since the vehicle is California Emissions.

posted 06-30-2005 12:27 PM               

SAE DTC P0125=Coolant Temperature Insufficient for Closed Loop Operation.
Manufacturer DTC P1135 (for Toyota) means A/F Sensor Heater Circuit Malfunction Bank 1 Sensor 1 (Set when the heater operates, heater current exceeds 8A or heater current of 0.25A or less).
The A/F sensor contains a ECU-controlled heater. At start-up, the heater helps warm the A/F sensors to quickly operating temperature. With minimal exhaust gas flow, the heater keeps the A/F sensor from cooling down.
Take a look http://www.babcox.com/editorial/us/us10226.htm
Checking Resistance.
a. Disconnect the A/F sensor connector.
b. Using an ohmmeter measure the resistance between terminals +B and HT. Resistance: 0.8 - 1.4 ohms at 20°C (68°F). If the resistance is not as specified, replace the sensor.
Torque: 44 Nm (440 kgf.cm, 31 ft.lbf)
c. Reconnect the A/F sensor connector.
(http://www.alflash.narod.ru/O2/79062351.gif )
Quotes.
P0125 set if after the engine is warmed up, A/F Sensor Output* does not change when conditions (a), (b), (c), and (d) continue for at least 1.5 min.:
a. Engine speed: 1,500 rpm or more
b. Vehicle speed: 25 – 62 mph (40 –100 km/h)
c. Throttle valve is not fully closed
d. 140 sec. or more after starting engine
*Output values changes inside ECM only
This DTC can be set due to other related parts failure.
HTH,