Troubleshooting — General Information (Audi Q7-4L-D)

Note: Refer also to the Troubleshooting section of the Introduction.

1. The fuel system is a component of the engine management system, so some of its components can also perform functions related to the fuel system.

2. When a failure is detected, the control unit records the corresponding DTC code in its memory, which can be read using a special scanner.

Note: Remember to clear the control unit memory after reading fault codes and making the appropriate corrections.

3. Reading the information stored in the ECM memory in most cases allows us to determine the causes of engine malfunctions. Analysis of read information using a list of codes (see Specifications) allows you to localize the source of failure at the level of a specific element or its wiring circuit.

Attention: A visual inspection of the wiring and connectors is not enough - be sure to read the information stored in the control unit memory!

4. DTC codes are five-digit codes and can be identified by their alphanumeric structure. The code structure is described below using P0401 as an example (eGR adjustment, too much air mass):

1st sign

R - engine and transmission (Powertrain);
B - Body;
C - Chassis;
U - data transmission systems.

2nd sign

0 - standardized code (SAE/ ISO);
1 - code assigned by the manufacturer;
2 - standardized code (SAE/ ISO);
3 - distributed area for standardized codes (SAE/ISO) and for codes assigned by the manufacturer.

3rd sign

0 - fuel and air supply metering, additional equipment that reduces exhaust toxicity;
1, 2 - dosing of fuel and air supply;
3 - ignition system (gasoline models);
4 - additional equipment that reduces exhaust toxicity;
5 - driving speed, idle parameters and other input data;
6 - on-board computer and other output data;
7-9 - gearbox;
A - combined drive.