- check for fault codes;
- control of data transmission from the ECU.
ECU fault codes are divided into current and non-permanent. Current fault codes are faults that are currently active, while non-permanent fault codes are faults that are not currently detected but have been previously recorded by the system. The table below shows the main ECM fault codes.
| Code malfunctions | Possible problem node or chain |
| DF001 | Coolant Temperature Sensor Circuit |
| DF002 | Air temperature sensor circuit |
| DF022 | On-Board Diagnostic System Warning Light Circuit |
| DF038 | ECU operation |
| DF040 | Cylinder 1 injector circuit |
| DF041 | Cylinder 2 injector circuit |
| DF042 | Cylinder 3 injector circuit |
| DF043 | Cylinder 4 injector chain |
| DF081 | Evaporative Canister Purge Solenoid Valve Circuit |
| DF082 | Oxygen Sensor Control Heating Circuit |
| DF083 | Oxygen Sensor Diagnostic Heating Circuit |
| DF084 | Control circuit of the relay of the actuators of the ECU |
| DF091 | Vehicle speed information |
| DF092 | Oxygen Sensor Control Circuit |
| DF093 | Oxygen Sensor Diagnostic Circuit |
| DF123 | Fuel mixture misfires |
| DF232 | Refrigerant Pressure Sensor Circuit |
| DF328 | Throttle Position Sensor Circuit |
| DF330 | Knock sensor circuit |
| DF336 | Crankshaft speed sensor circuit |
| DF352 | Anti-theft system chain |
| DF353 | Absolute pressure sensor circuit |
| DF360 | IAC chain |
| DF361 | Ignition coil circuit for cylinders 1 and 4 |
| DF362 | Cylinder ignition coil circuit 2 of |
| DF514 | Fuel Pump Relay Circuit |
| DF587 | Sensor power supply circuit - 5 V |
Common ECU malfunctions and recommendations for their elimination
Error codes DF001, DF002 - malfunction of the air temperature sensor. You should check the integrity of the sensor connections, short circuits to the power supply and ground, and the sensor itself.
Error code DF038 - ECU operation error. Check the ECU software and the ECU itself for compliance (hardware, better by replacing with a known good one).
Error codes DF040 - DF043 - error of the corresponding injectors. They check the integrity of connections, possible short circuits in circuits and the operation of injectors.
Error code DF082 - control sensor error. Check for possible short circuits and the condition of the connectors and electrical wiring of the sensor, as well as the functionality of the sensor by replacement.
Error code DF123 - misfire. They check the operation of injectors, spark plugs, ignition coils, etc.
Error code DF232 - refrigerant pressure sensor error. They check the integrity of connections, possible short circuits, and the operation of the sensor.
Error code DF336 - Crankshaft position sensor malfunction. They check possible short circuits and the condition of the connections, the reliability of the sensor fastening and its functionality.
Error code DF360 — IAC error. Check the operation of the IAC and its circuits, the reliability of the attachment to the pipe.
Error code DF394 - catalytic converter error. They check the tightness of the exhaust system, perform a visual inspection of the catalyst design, and check the consumption of engine oil and coolant. Most likely, the catalytic converter failed due to poor quality fuel.
Troubleshooting for intermittent faults
First, it is necessary to check for possible problems with electrical circuits. Particular attention should be paid to the following:
- no deformations on terminal connections;
- reliability of mechanical crimping of terminals with wires;
- no cracks, signs of damage, or melting on the pad housings.
After turning on the ignition and starting the engine, it is necessary to move the wire harnesses, starting from the connectors and along the harness, while monitoring the operation of the ECM using a diagnostic device. If a fault is detected in the wiring harness, it must be corrected.
Checking the operation of the ECU ECM
The performance of the ECU is checked using a diagnostic device, while it is switched to the "Parameters" - "General view" mode.
If the message "The anti-theft system is active" appears during diagnostics, you should check the operation of the standard anti-theft device.
On-board diagnostics system
The vehicle's ECU has an on-board diagnostics system, which includes a warning lamp in the instrument cluster that lights up when it detects that the exhaust gas toxicity threshold has been exceeded, and also notifies the driver of the need for repair work.
The on-board diagnostics system includes the following types:
- misfires of the fuel mixture;
- oxygen sensor control;
- control of ECU elements;
- catalyst control.
The on-board diagnostics warning lamp turns on when the on-board system detects the same fault over several trips or engine starts, or when faults are detected in electrical circuits.
The on-board diagnostics warning light flashes when misfires in the fuel mixture are detected. This emergency situation leads to failure of the catalytic converter.
Information about faults is entered into the non-volatile memory of the ECU; this information is deleted automatically after 40 subsequent tests, as well as using a diagnostic device.
Diagnostics of the operation of the electronic anti-theft engine start lock
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The ECU of the Lada Largus vehicle includes an electronic anti-theft engine start blocking system (EATSB), which prevents unauthorized engine starting by breaking the ECU control circuits.
In turn, the ECU has the ability to individually code the digital signal generated by the EBPZD control unit to permit or prohibit engine starting.
The EPBZD or immobilizer is an electronic device that includes an electronic control unit with a communication coil on the ignition switch, a control lamp located on the dashboard (figure 2) and keys with radio frequency remote control.
The electronic control unit of the EPBZD is connected to the ECU of the ECM via a diagnostic line, which is switched by a relay (is part of the control unit).
If the diagnostic tool is not connected to the diagnostic socket, the diagnostic line is used to communicate between the ECM and the EBD electronic control unit. When the diagnostic tool is connected, the line automatically switches to communication between the ECM and the diagnostic tool. It should be noted that the ECU has priority over the diagnostic device - in the event of information exchange between the ECU and the ECU, the connection between the ECU and the diagnostic device is broken.
The control unit of the electronic fire alarm system is installed under the vehicle's dashboard.
Activation of work, error codes and diagnostics of malfunctions of the EPBZD system
The ECU control unit. The ECU and ignition key are supplied by the manufacturer in an uncoded form. Therefore, after installing them on the vehicle, it is necessary to activate the electronic engine start blocking system.
It is necessary to take into account that after activation, the ignition key and the control unit of the electronic anti-theft alarm system will work only on this vehicle; it is impossible to remove the activation or re-code the system.
The activation procedure of the EPBZD system is performed using a diagnostic device with preliminary flashing of the activation code from the PC memory.
During the procedure for activating the ECU code, data is exchanged with subsequent comparison of the information stored in the ECU memory with the code transmitted from the diagnostic device. One of the main stages of verification is the comparison of the VIN code data of the vehicle, which is individual for each vehicle.
Diagnostics of malfunctions of the EPBZD system
Just as when checking for the presence of ECM error codes, the error codes of the EPBZD system are detected. A diagnostic device is connected to the diagnostic socket, after which the error codes are read.
We will provide the main error codes, example malfunctions and methods for their elimination.
Error code DF055 - Coded line circuit. Most likely, the connection between the electronic control units of the ECM and the ECU is broken - check the connection between contact 40 of the ECM and contact 58 of the ECU.
Error code DF059 - there is no communication between the electronic unit of the EPBZD and the ECU. Check the condition of the contacts and the reliability of their connections, as well as the corresponding circuits for short circuits with +12 V or to ground. After troubleshooting, you should delete the error codes from the ECU memory.