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 1.7v@20mA LED
D2 1.7v@20mA LED

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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

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

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
Copyright OBD-Codes.com

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

1 Answer

'01 Sequoia throwing 2 OBD II codes: po125 & po135. replace pre-cat o2 sensor?


DTC P0125 OBD-II - Insufficient Coolant Temperature For Closed Loop Fuel Control
This means that the engine coolant temperature (ECT) sensor indicates that the engine has not reached the required temperature level to enter closed-loop operation within a specified amount of time after starting the engine. You will likely not notice any drivability problems.

A code P0125 may mean that one or more of the following has happened:
Insufficient warm up time
Low engine coolant level
Leaking or stuck open thermostat
Faulty coolant temperature sensor


DTC P0135 OBD-II - Oxygen O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
This code refers to the front oxygen sensor on Bank 1. The heated circuit in the oxygen sensor decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The ECM tracks how long it takes for the oxygen sensor to begin switching. It the ECM determines (based on coolant temp) that too much time elapsed before the oxygen sensor began operating properly, it will set P0135. You will likely notice poor fuel economy the illumination of the MIL.

A code P0135 may mean that one or more of the following has happened:
O2 Heater element resistance is high
Internal short or open in the heater element
O2 heater circuit wiring high resistance
open or short to ground in the wiring harness


For additional details, feel free to contact us in the preivous code link.

Hope this helps; also keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using Fixya, and have a nice day.

Oct 12, 2011 | 2001 Toyota Sequoia

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