EGR fault induced limp mode

Hi guys, thanks for the great course. You guys should start training at industry level, far superior to what’s currently on offer to the trade. Your course effortlessly answered so many questions that I’ve really struggled to find answers to. Anyway, my question for the you is: diesel Isuzu’s, Toyota’s and some Fords drop into what seems to be a limp mode when they log an EGR reduced flow code - is this actually a limp mode or a calculation error causing the ecu to shut off the throttle body in order to try and compensate for a blocked or jammed EGR?

Any ideas guys?

Hey Stu,

Each manufacturer has their own strategy in relation to how they respond to each condition (ie. stuck open, blocked, stuck shut etc)

The systems i have worked with monitor the EGR position (how open it is) and monitor the relation in change to mass air flow.

So in normally functioning system, opening the EGR will allow recirculated exhaust gas to be introduced into the intake charge. The more open the EGR is, the more flow. The more exhaust gas introduced will reduce the flow on the intake, resulting in a lower airflow meter reading.

As an EGR (usually EGR cooler) blocks up, the system has less of an influence on the mass airflow when the EGR is in operation.

Usually for blocked EGR errors, they have progressive strategies in place for power reduction based of calculated blockage, or distance driven with error logged.

In the case of Jammed EGRS, they will not close the throttle, but reduce aim boost, and fuel mass injected to reduce power.