• Tiny
  • yvonnelw
  • 1997 Toyota Camry
  • 13,061 miles

My 1997 toyota camry check engine light came on, I took it in to Firestone auto place and they came up with some codes PO171 System TOO LEAN, PO130 AIR CONTROL MALFUNCTION. Please help to determine what it is and the cost of fixing. Than you

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Saturday, November 24th, 2012 AT 10:25 PM

2 Replies

  • Tiny
  • ASEMaster6371
  • Expert
  • 25,556 posts

DTC P0130 Heated Oxygen Sensor Circuit Malfunction
(Bank 1 Sensor 1) (Without California Emissions.)

Oxygen Sensor Cut-Away

Reference Chart

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 heated oxygen sensor has the characteristic where by its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This is used to detect the oxygen concentration in the exhaust gas and provide feedback to the computer for control of the air-fuel ratio.
When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the heated oxygen sensor informs the ECM of the LEAN condition (small electromotive force: 0 V).
When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio the oxygen concentration in the exhaust gas in reduced and the heated oxygen sensor informs the ECM of the RICH condition (large electromotive force: 1V).
The ECM judges by the electromotive force from the heated oxygen sensor whether the air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the heated oxygen sensor causes output of abnormal electromotive force, the ECM is unable to perform accurate air-fuel ratio control.
The heated oxygen sensors include 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.


HINT : Sensor 1 refers to the sensor closer to the engine body.
The heated oxygen sensor's output voltage and the short-term fuel trim value can be read using the OBD II scan tool or TOYOTA hand-held tester.


(1) Connect the TOYOTA hand-held tester to the DLC3.
(2) Switch the TOYOTA hand-held tester from normal mode to check mode.
(3) Start the engine and warm it up withe all accessory switches OFF.
(4) Drive the vehicle at 50 65 km/h (31 40 mph) for 1 3 min. To warm up the heated oxygen sensor.
(5) Let the engine idle for 1 min.

HINT : If a malfunction exists, the MIL will light up during step (5).

NOTICE : If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.
If you do not have a TOYOTA hand-held tester, turn the ignition switch OFF after performing steps (3) to (5), then perform steps (3) to (5) again.

Step 1

Step 2

Step 3

171 is a lean code. Could be vacuum leak, pcv valve, mass air flow or low fuel pressure.


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Saturday, November 24th, 2012 AT 11:01 PM
  • Tiny
  • yvonnelw
  • Member

Thank you so much, now I know what's up.

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Sunday, November 25th, 2012 AT 4:51 AM

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