Service Drive Cycles

There are six Test Modes as follows:

• Mode 1 – Parameter Identification (PID) is used for the accessing of live data such as digital

and analogue values of inputs and outputs.

• Mode 2 – Freeze Frame Data Access, provides a snapshot of data which is captured for all

emissions related values at the time a fault is detected.

• Mode 3 – This enables all scan tools to retrieve stored DTCs. The scan tool used may store

the DTC code alone, or with descriptive text.

• Mode 4 – This is the ability of the scan tool to clear all emission-related diagnostic

information. When the ECM’s memory is reset, an Inspection/Maintenance Readiness code

will be stored (e.g. P1000 indicates that the ECM is awaiting further vehicle operating modes

to complete on-board monitoring and testing).

• Mode 5 – This is the actual monitoring of the HO₂ sensors to determine Catalytic Converter

efficiency.

• Mode 6 – The Output State Mode (OTM) allows the technician to energise and de-energise

many of the output devices that are controlled by the ECM to determine their correct operation

and real-time functionality.

Service Drive Cycles

To ensure that a fault causing a diagnostic trouble code (DTC) has been successfully resolved, drive cycles have to be carried out. Testbook indicates the relevant drive cycles to be carried out following the incidence of a specific P-code.

A driving cycle consists of engine start-up, vehicle operation (exceeding starting speed), overrunning and engine stopping. On OBDII, a drive cycle is simply defined as starting the engine and driving the vehicle long enough to raise the coolant temperature by at least 40° F (if the startup temperature is less than 160° F).

A complete driving cycle should perform diagnostics on all systems.

Drive Cycles take the warm-up cycle one step further by operating the vehicle to the point whereby it will go into closed loop and include the operating conditions that are necessary to initiate or complete a specific OBD-II monitor or it will verify a symptom or its repair.

The OBD-II Drive Cycle is a very specific combination of driving conditions that have been set out by the Federal Clean Air Act. For a complete OBD-II trip to occur, it is necessary for the vehicle to travel a specified distance to give the system time to complete all the necessary tests on:

• Misfires
• Fuel System
• Electrical components
• Exhaust Gas Recirculation (where applicable)
• HO₂ Sensors