Tech Info on 02 (Lambda or Oxygen) Sensors + Wiring Colours

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calnorth
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Tech Info on 02 (Lambda or Oxygen) Sensors + Wiring Colours

Post by calnorth » Sat Jan 02, 2021 9:45 am

As Emissions Regs get tighter so do exhaust sensor requirements. 4 Cyl Engines commonly have two O2 sensors and each placed either side of the Cat Converter. The first (upstream) is early in the exhaust to control (via ECU) air/fuel mix and is before the Cat Converter. The second (downstream) is after the Cat Converter and checks (via ECU), CAT efficiency. We see DTC's PO135 for upstream errors and PO136 for downstream errors. O2 sensors like clean engines and exhausts that are not "leaky". Exhaust contamination spoils them (oil, anti-freeze etc).

Below is a technical post on O2 sensors. Not completely comprehensive but very informative. The lambdapower.com site is a very good read. Contact them if in difficulty as scheduled O2 sensor change (mileage) is important to know for instance......I am not a promoter.

Technical info/(types) - https://secure.lambdapower.co.uk/TechNo ... _index.asp

Diagnostics - https://secure.lambdapower.co.uk/diagno ... _index.asp

4 wire Zirconia types are (were... :roll: ) the most common 02 Sensors and illustrates wiring colour codes - J10 appears to use 4 wire O2 sensors.

5 wire Wideband 02 sensors - concerns "Oxygen Levels in Exhaust" detection and ECU control of fuel/air mixture with Cat Converter efficiency checks. The measurement is of O2 in exhaust gas against free external air. Its a current common type of O2 sensor and related to tighter emissions requirements. This sensor type is fairly complicated and heated to work at 600 deg C so we may expect periodic trouble. An electronic comparator circuit resides within the ECU....its an O2 watchdog. No life data is provided by manufacturers (Bosch, NGK, Denso) that I can find. Earlier 4 wire O2 sensors were changed (scheduled) at about 70k miles. 5 wires colours shown last below. 5 wire applicable to J11b 1.6 engines and most others I suspect.

https://www.autoserviceworld.com/jobber ... explained/

More detail: https://www.aa1car.com/library/wraf.htm

5 wire "Pump" Cell: (wideband complication starts here)

A Planar Air Fuel Sensor is a combination of a standard Zirconium Oxide Oxygen sensor and a Pump Cell to maintain a constant sensing of a stoichiometric air fuel ratio through the extreme rich and lean conditions. The pump cell is a diffusion gap in the Zirconium Oxide of the sensor that is connected to a control circuit. The pump cell controls the oxygen concentration of the sensor by adding or subtracting oxygen to the diffusion gap. Input to the electronic circuit modifies the oxygen concentration by changing the polarity of the current flow in the pump cell. The changing polarity of the input and trim current flow causes the control circuit to send a rich or lean signal to the engine control module.

Thermal Shock: An earlier post mentioned failure of the 5 wire O2 sensor heater control: (early sensor heater failure...beware)

The first image below shows the major parts of the heater control circuitry. It is more complex than the Lambda (oxygen) measuring circuitry. Op-amp E, with the aid of a very low ohms resistor, can directly measure the current through the heater and this is used during warm-up to control the average heater power to within close limits (as specified in sensor manufacturers' documentation). The heater current and battery voltage (Vbatt) can also be used (via Ohm's Law) to calculate a rough heater temperature. When the sensor is warm enough for it's Vs sense cell impedance to be measured directly a more accurate temperature measurement can be made. Small voltage pulses are applied to Vs using driver F and again Ohm's law is used to calculate the sense cell impedance by measuring various voltages with op-amp D. The heater is switched, at around 30 hz, using a low-side FET driver and the heater PID control algorithm. PID = Proportional–Integral–Derivative controller. A micro-controller implementation.
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Screenshot 2021-01.png

Screensh.png

O2 Lambda wiring.png

Last edited by calnorth on Sun Jan 03, 2021 12:42 pm, edited 5 times in total.
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lewisbryant
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Re: Tech Info on 02 (Lambda or Oxygen) Sensors + Wiring Colours

Post by lewisbryant » Sun Jan 03, 2021 12:13 am

Very technical post, I like it 👍

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calnorth
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Re: Tech Info on 02 (Lambda or Oxygen) Sensors + Wiring Colours

Post by calnorth » Sun Jan 03, 2021 9:04 am

lewisbryant wrote:
Sun Jan 03, 2021 12:13 am
Very technical post, I like it 👍
Thanks @lewisbryant. Its a fairly quick story on the subject that seems to raise its ugly head here fairly often. The deeper tech story on 5 wire O2 sensors is as link below and goes down into the long grass. It is a well understood industrial function I had forgotten. I have to wonder how far down they can push emissions using these sensors. The electronics is not an issue but certainly the analogues (materials) are. Ev will eliminate the issue at the user point and simply shift the problem elsewhere - nearby.

https://www.wbo2.com/lsu/lsuworks.htm
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