Wave Length specs for O2 Sensors

[SKJRunner01]

Hey guys,
I am trying to figure out the wave length specs for the front vs the rear O2 sensors on my 01 4Runner. I have code PO171 and the shop has done ever test you can think of, from MAF Sensor to Cat. They are replacing the fuel pump thinking this might do it. They have noticed that the front O2 is laggy when they measure the voltage waves... Is this normal?

:hail: Please help

 

[19963.4lsr5]

Here is a good description of the too lean code

Here's what the Factory Service Manual has to say;

P0171
(DI–193)
System too Lean (Fuel Trim)
Air induction system
Injector blockage
Mass air flow meter
Engine coolant temp. sensor
Fuel pressure
Gas leak on exhaust system
Open or short in A/F sensor (Bank 1 sensor 1) circuit
A/F sensor (bank 1 sensor 1)
ECM

CIRCUIT DESCRIPTION
Fuel trim is related to the feedback compensation value, not to the basic injection time. Fuel trim includes short–term fuel trim and long–term fuel trim.
Short–term fuel trim is the short–term fuel compensation used to maintain the air–fuel ratio at its ideal theoretical value. The signal from the A/F sensor is approximately proportional to the existing air–fuel ratio, and ECM compares it with the ideal theoretical value, the ECM reduces fuel volume immediately if the air–fuel ratio is RICH and increases fuel volume if it is LEAN. Long–term fuel trim compensates for the deviation from the central value of the short–term fuel trim stored by each engine tolerance, and the deviation from the central value due to the passage of time and changes of environment.
If both the short–term fuel trim and long–term fuel trim exceed a certain value, it is detected as a malfunction and the MIL lights up.

HINT:
When the DTC P0171 is recorded, the actual air–fuel ratio is on the lean side. When DTC P0172 is recorded, the actual air–fuel ratio is on the rich side.
If the vehicle runs out of fuel, the air–fuel ratio is lean and DTC P0171 is recorded. The MIL then comes on.
If the total of the short–term fuel trim value and long–term fuel trim value is within ± 35 % (80°C (176°F) or more), the system is functioning normally.
The A/F sensor (bank 1 sensor 1) output voltage and the short–term fuel trim value can be read using the OBD II scan tool or TOYOTA hand–held tester.
The ECM controls the voltage of the terminals AF1+ and AF1– of the ECM to the fixed voltage. Therefore it is impossible to confirm the A/F sensor output voltage without OBD II scan tool or TOYOTA hand–

 

[SKJRunner01]

This is becoming a headache

So,
Truck is in the shop. They tested all they can. The first "give it a go" was replacing the fuel filter. They reset the ECU, drove it around, the engine light came back on before the redesness sensors reset! What is going on?! :noidea:

 

[Nelsonmd]

Download the FSM (linked from this forum, just look for it) and check out their diagnosis procedure. That should minimize the "replace and re-check" strategy that makes so much money for the shops.

 

[LittleCaesar]

So they have not replaced either O2 sensor yet?

Follow Nelsonmd's advice and you should be fine.

 

[19963.4lsr5]

Exhaust manifold leaks could cause it also.

 

[Ed_C]

The signal seems laggy because it's an air fuel ratio sensor,it won't have the same signal as a standard O2 sensor http://www.autoshop101.com/forms/h37.pdf