HO2S – Heated Oxygen Sensor. IAT – Intake Air Temperature. ISO – International Standards Organization OBDII communication mode, used by Chrysler. List of supported OBD-II parameters and sensors by OBD Auto Doctor OBD2 scantool software. $14 – $1B, Oxygen sensor output voltage, Short term fuel trim. Oxygen Sensor Drive Cycles The following are some sample drive cycle requirements for the oxygen sensor monitor to run: Ford: The monitor should run when.

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You need to learn how to distinguish good waveforms from bad ones – which means looking at vehicles that do not have problems as well as ones that do.

You may hear the word ‘probe’ substituted for ‘sensor’ – eg. When a fault occurs, OBD II logs a code and records all related sensor values at that moment for later analysis. This mode retrieves “Freeze frame data”. System Too Lean Bank 2. When used in environments with an extremely high level of electromagnetic noise, the Bluetooth module can be unplugged, and replaced with a serial cable.

GM Driving Cycle 3.

Lambda Sensors – HEGO, EGO, and other terminology

Header Byte 1 — Bits [ Newsletter Signup Register Now. The second part runs after the vehicle has sit for 8 or more hours cold soak ehgo being driven. Unlike earlier OBD systems that only set a diagnostic trouble code DTC when a sensor circuit experienced a gross failure such as a short, open or over voltage, OBD II sets codes if a fault has the potential of causing emissions to rise.

The algorithms for running these eight, ‘periodic’ monitors are unique to each manufacturer and involve such things as ambient temperature as well as driving conditions. This is data can be different between vehicle model years and will be different between vehicle manufacturers. How can we help?


Executes the EGR Monitor. If this happens on two consecutive trips, the Check Engine light will come on and flash to alert the driver when the misfire problem is occurring. Newly launched model with wider vehicle coverage, as it supports the CAN Protocol.

Things like short term fuel trim, throttle position and engine speed can change and not be correct in freeze frame data. If the P code must be cleared in these conditions, the PCM must detect them once twice on some applications before the EVAP monitor can be “bypassed” and the P cleared. This data is a subset of the items in mode 1, but was stored at some point in the past when a trouble code was set.

Most times freeze frame data is stored over a period of several seconds. To complete a specific monitor for repair verification, follow steps 1 through 4, and then continue with the step described by the appropriate monitor found under the “OBD-II Monitor Exercised” column.

Example of the DLC location Figure This will complete the second half of the monitor that checks the responsiveness of the O2 sensors. However, be aware that there is a possibility of the lean condition being caused by a leak in the intake system.

OBD II Engine Diagnostics

Peter 40 years of experience. The target is the device on the bus that you wish to address. Cost of diagnosing the P code. Instead of the first byte being a priority, the first byte is in the format 1 1 L L L L L L, where the L’s is a 6 bit number representing the length of the data packet being sent.


OBD-II Acronyms and Jargon Like any government instigated project, OBD-II quickly became a mouse’s nest of acronyms, jargon, shorthand and code phrases that have meaning heog the select few and sometimes seem to uego to keep the rest of us at bay.

Oxygen sensor – referring to the fact that the Lambda Sensor measures the Oxygen present in the exhaust gas stream O2 sensor – back to school for this one – O2 is the chemical symbol for an Oxygen molecule. More From Drivability The importance of asking ‘why?

Another view to the connector itself is shown in figure Allow the “bypass” counter to increment to two. These are the “non-continuous” monitors and include the catalytic converter efficiency monitor, the evaporative system monitor that detects fuel vapor leaks in obs fuel system, the EGR system monitors, the secondary air system monitor if the vehicle has such a systemand the oxygen sensor monitors.

Driving Cycle is a series of data points representing the speed of the vehicle besides some other parameters versus time. Oxygen sensor output voltage, Short term fuel trim Bank 1 – 4: Stop and idle for 4 minutes.

The 10 modes of OBDII

Today the CAN bus is also used as a field bus in general automation environments: Sensor 1 – Sensor 2. There is a separate section with more on catalytic converters later.

Determines if any monitor has not completed. Sensor 1 – 4. The MIL is only ond to extinguish when the same fault has not been detected on three successive driving cycles.