1999 Toyota Rav4 MIL on, codes P0171 & P1133

  • 1999 TOYOTA RAV4
Engine Performance problem
1999 Toyota Rav4 4 cyl Two Wheel Drive Automatic 109K miles

Codes: P0171 (lean bank 1)
P1133 (A/F sensor ckt. Response fault B1-S1)
New parts: Nippondenso plugs, fuel filter, air filter, updated air/fuel ratio sensor

Freeze frame data:
RPM 1935
Fuel sys. CL loop
IAT 97deg F
Coolant 185deg F
STFT 24.2%
LTFT 44.5%

Fuel pressure 49-50 psi
Completely checked over for vacuum leaks
Tested MAP per Alldata instuction, passed
Exhaust back pressure test, 1/2psi @2500rpm
Thoroughly inspected & ohmed wiring from sensor to ecm, including grounds
This vehicle does not have a Mass Air Flow

I am a technician working at an independent shop. This is my father’s Rav4 & it’s giving me fits. MIL would come on intermittently at first with loss of power and rough idle. Searched TSB’s. Found bulletin# EG012-01 for code P1133. Installed updated Air/Fuel ratio sensor, (new plugs, fuel filter, & air filter couple of weeks earlier).
All was well for about 6 months then MIL came back on, same codes & very intermittent so he kept driving. Meanwhile I was checking everything I could think of when I could get the rav4 away from him. It finally got too bad to drive, so I traded cars with him. I drove around with my scanner hooked up for 7 days before it finally acted up big time. A/F ratio voltage was stuck lean at about 3.8v to 4.0v, which Snap on’s scanner doesn’t list in freeze frame. The fuel trims were high.(See freeze frame data) Engine would barely idle, and even though sensor showed lean when I walked behind the vehicle there was black smoke was rolling out of the exhaust. At this point I pretty much ruled out a vacuum problem.
I re-ohmed & inspected the sensor to ECM wiring, so this time I tapped into AF+ and AF- at the sensor harness. AF+ was steady at 3.3V and AF- at 3.0V which is normal for this system. Even when engine would barely idle, these two voltages did not vary. In my mind that confirms the wiring from the ECM to the sensor is good. Called Toyota & got another A/F sensor. All was well for about 3 months & now the MIL is on again, same codes, same symptoms, but like last time, start out mild and I’m sure will continue to get worse. Am I missing something? Do I install a 3rd sensor? There have been 2 bulletins concerning code p1133, one in 1999 & the other in 2001. Both had updated A/F sensors. I am hesitant to go for the ECM because of the fact that a new sensor will go 3 to 6 months trouble-free, and then gradually gets worse almost to the point where it’s not drivable. Any help would be appreciated.
Do you
have the same problem?
Thursday, February 4th, 2010 AT 10:55 PM

1 Reply

This is a known problem, A tech bulliten is out for 98-00 Rav4's Here it is:




Was this
Friday, February 5th, 2010 AT 3:28 PM

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