Tip & How-To about Mitsubishi Eclipse

How to make your own O2 Sensor Simulator!

What is an O2 sensor simulator?
The OBD-II cars (1996-1998) have two O2 sensors to measure the amount of oxygen in the exhaust gas. First sensor is measuring it right after gases escape engine and this data is used to adjust fuel trim of the engine, as well as catch some faulty conditions. The second sensor is located after the catalic converter, and is used to detect the health of catalic converter. The ECU expects the signal from the sensor to be oscillating from below 0.4v to above 0.6v, but not above 1.2v, every few seconds while driving.

If you install an aftermarket downpipe with no cat (which is for off-road applications only) the ECU will detect this and indicate an error (MIL). The You can reset the ECU to clear the error code.

How to build Your Own Oxygen Sensor Simulator!
The rest of the page shows how to build an oscillating signal generator with just the right frequency and voltage to fool the ECU. It is based on classical astable operating mode of 555 timer.

Don't attach it directly to the ECU right after assembly. Instead attach it to the battery and check the output. You should get approximately 0v/0.7v flipping about every 3.3 seconds when the car is not running, and 0v/0.9v when the car is running. The current should stay below 10mA.

One LED should be always on whenever the power is supplied. Another LED indicates when the output signal is high, so it should go on and off with the signal.

When tapping the ECU wires, check everything before hooking up the oscillator. The power source should read 0v when the key is removed, about 12.6v when they key is at ACC and about 14.3 when the alternator is running. The resistance between ground wire and the body shield of the ECU should be 0 ohms. And it would be best if you run the car and monitor the voltage of the original oxygen sensor wire before cutting it to make sure you have indeed got the right one. The resistance between ECU PIN #47 and ground is about 1.3 to 1.6 M Ohm.

The original sensor should still be dangling around, or plugged into the downpipe. The reason is that ECU also monitors the resistance of heater circuit inside the sensor. If you want to COMPELTELY disconnect it, you will need to measure the resistance of the heater circuit and install the right resistor between ECU PIN #72 and ECU PIN #31 Anyway, there is no need to do it if you just leave O2 sensor alone and only intercept the oxygen signal wire.

Components
R1 100 K Ohm
R2 1 M Ohm
R3 100 K Ohm
R4 10 K Ohm
C1 4.7 uF
C2 22 uF
D1 [email protected] LED
D2 [email protected] LED

I assume no responsibility for any kind of damages.

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4 Answers

I have 96 buick code p0420.I have replaced the converter and both 02 sensors.mil came back on code p0420. do not know what to do next, help.


fault code that is set when the Onboard Diagnostic II (OBD II) system sees a drop in converter efficiency. The OBD II system monitors catalyst efficiency by comparing the switching activity of the upstream and downstream oxygen sensors in the exhaust. The upstream O2 sensor in the exhaust manifold reflects the condition of the exhaust gases as they exit the engine. The downstream O2 sensor in or behind the catalytic converter reflects the condition of the exhaust after it passes through he converter.

Aug 02, 2008 | Buick Regal Cars & Trucks

1 Answer

Got the engine management light on, had someone check it out for me come back with p0420? Whats the most likely problem? Daewoo kalos 52 plate


A P0420 diagnostic trouble code is a "generic" fault code that is set when the Onboard Diagnostic II (OBD II) catalyst monitor detects a drop in converter efficiency. The OBD II system monitors catalyst efficiency by comparing the switching activity of the upstream and downstream oxygen sensors in the exhaust. The upstream O2 sensor in the exhaust manifold reacts to the exhaust gases as they exit the engine. The downstream O2 sensor in or behind the catalytic converter reacts to the exhaust gases as they exit the converter.

Mar 31, 2017 | Daewoo Cars & Trucks

1 Answer

Code P0157


OBD II P0157 due to Oxygen Sensor Circuit Low Voltage (Bank 2, Sensor 2)
This code refers to a fault in the post-catalyst o2 sensor on Bank 2. First, a basic run-down of the catalyst: The Catalytic Converter is used to help control tailpipe emissions, to "clean up" the exhaust, if you will. The PCM (Powertrain Control Module) uses the signal from the heated oxygen sensor to the rear of the catalyst to monitor the catalyst's efficiency by comparing it to the o2 sensors in front of the catalyst.

Read more at: http://www.obd-codes.com/p0157
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P0157 O2 Sensor Circuit Low Voltage

Mar 11, 2016 | 2007 Honda Odyssey

1 Answer

I need to know the code dtc44 for a 1990 Buick Century


GM OBD Trouble Code 44

Auto Systems and Repair

Oxygen Sensor Error (Lean Condition Indicated) The ECM receives a signal from the O2 sensor based on the amount of oxygen in the exhaust. If there is excess oxygen in the exhaust, it is in lean condition and the O2 sensor voltage will be low. The ECM uses this information to adjust the amount of fuel delivered to each cylinder.
Fault Code Description
  • 44 - Oxygen sensor error (lean condition indicated)
  • On V-type engines with two O2 sensors, code 44 would indicate the left bank sensor is lean
Symptoms
  • Lack of power
Common Problems
  • Faulty O2 sensor
  • Engine vacuum leak

Dec 01, 2014 | Buick Cars & Trucks

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