- checking for fault codes;
- control of data transfer from the computer.
ECM trouble codes are divided into current and non-permanent. Current fault codes are currently active faults, and intermittent faults are faults not currently detected, but previously recorded by the system. The table below lists the main ECM trouble codes.
| Code malfunctions | Possible problem node or chain |
| DF001 | Coolant temperature sensor circuit |
| DF002 | Air temperature sensor circuit |
| DF022 | OBD 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 circuit |
| DF081 | Canister Purge Solenoid Valve Circuit |
| DF082 | Control oxygen sensor heating circuit |
| DF083 | Diagnostic oxygen sensor heating circuit |
| DF084 | ECM Actuator Relay Control Circuit |
| DF091 | Vehicle speed information |
| DF092 | Control oxygen sensor circuit |
| DF093 | Diagnostic Oxygen Sensor Circuit |
| DF123 | Misfire fuel mixture |
| DF232 | Refrigerant Pressure Sensor Circuit |
| DF328 | Throttle position sensor circuit |
| DF330 | knock sensor circuit |
| DF336 | crankshaft speed sensor circuit |
| DF352 | Anti-theft circuit |
| DF353 | Absolute Pressure Sensor Circuit |
| DF360 | IAC circuit |
| DF361 | Cylinder 1 &4 Ignition Coil Circuit |
| DF362 | Cylinder 2 Ignition Coil Circuit |
| DF514 | Fuel Pump Relay Circuit |
| DF587 | Sensor power circuit - 5 V |
Common ECM malfunctions and recommendations for their elimination
Error codes DF001, DF002 - malfunction of the air temperature sensor. It is necessary to check the integrity of the sensor connections, short circuits to the power circuit and «mass» and the sensor itself.
Error code DF038 - ECU operation error. Check for compliance with the ECU software and the ECU itself (hardware, better by replacing a known good one).
Error codes DF040 - DF043 - error of the corresponding injectors. Check the integrity of the connections, possible short circuits in the circuits and the operation of the injectors.
Error code DF082 - control sensor error. They check possible short circuits and the condition of the connectors and electrical wiring of the sensor, as well as the operability of the sensor by replacing it.
Error code DF123 - mixture misfires. Check the operation of injectors, spark plugs, ignition coils, etc.
Error code DF232 - refrigerant pressure sensor error. Check the integrity of the connections, possible short circuits, the operation of the sensor.
Error code DF336 - violation of the crankshaft position sensor. They check possible short circuits and the condition of the connections, the reliability of the sensor mounting and its performance.
Error code DF360 - IAC error. Check the operation of the IAC and its circuits, the reliability of fastening to the pipe.
Error code DF394 is a catalytic converter error. They check the tightness of the exhaust gas system, visually check the design of the catalyst, check the consumption of engine oil and coolant. Most likely, the catalytic converter failed due to low-quality fuel.
Troubleshooting that is intermittent
The first step is to check for possible electrical circuit problems. Particular attention should be paid to the following:
- absence of deformations on terminal connections;
- reliability of mechanical crimping of terminals with wires;
- absence of cracks, traces of damage, melting on the bodies of the pads.
After the ignition is turned on and the engine is started, wiggle the wiring harnesses from the connectors and along the harness while monitoring the ECM with a scan tool. If a fault is found in the wiring harness, it must be repaired.
Checking the operation of the ECM
The operation of the computer is checked using a diagnostic tool, while it is transferred to the mode «Options» — «General View».
If a message appears during diagnostics «Anti-theft system active», you should check the operation of the standard anti-theft device.
On-Board Diagnostic System
The vehicle's ECM has an on-board diagnostic system that includes a warning light in the instrument cluster that illuminates when it detects that the exhaust gas toxicity threshold has been exceeded, and also alerts the driver to the need for repairs.
The on-board diagnostic system includes the following types:
- misfiring of the fuel mixture;
- control of the control oxygen sensor;
- control of ECM elements;
- catalyst control.
The on-board diagnostics warning light comes on if the on-board system detects the same malfunction during several trips or engine starts, as well as when malfunctions are detected in electrical circuits.
The flashing of the on-board diagnostics warning light occurs when a misfire is detected in the fuel mixture. This emergency leads to failure of the catalytic converter.
Information about malfunctions is entered into the non-volatile memory of the computer, this information is deleted automatically after 40 subsequent tests, as well as using a diagnostic tool.
Diagnostics of the operation of the electronic anti-theft engine start blocking
The ECM of the Lada Largus car includes an electronic anti-theft engine start blocking (EPBD), which prevents unauthorized starting of the engine by breaking the ECM control circuits.
In turn, the ECU has the ability to individually encode the digital signal generated by the EPBZD control unit to allow or prohibit the engine from starting.
EPBZD or immobilizer is an electronic device, which includes an electronic control unit with a communication coil on the ignition switch, a warning lamp located on the dashboard (pic. 2) and keys with RF remote control.
The EPBZD ECU is connected to the ECM via a diagnostic line that is switched by a relay (included in the control unit).
If the diagnostic tool is not connected to the diagnostic socket, the diagnostic line is used to communicate the ECM with the ECM. When a scan tool is connected, the line will automatically switch to exchange between the ECM and the scan tool. Please note that the EPBDD control unit has priority over the diagnostic tool - in the event of an exchange of information between the ECM and the EPBDD control unit, the communication between the ECM and the diagnostic tool is interrupted.
The EPBZD control unit is installed under the dashboard of the car.
Activation of work, error codes and diagnostics of malfunctions of the EPBD system
EPBZD control unit. The ECM and ignition key are shipped uncoded from the factory. Therefore, after installing them on the car, it is necessary to activate the electronic engine immobilizer system.
Please note that after activation, the ignition key and the EPBZD control unit will work only on this vehicle, it is impossible to remove the activation or re-code the system.
The procedure for activating the EPBDD system is carried out using a diagnostic tool with preliminary flashing the activation code from the PC memory.
During the EPBD code activation procedure, data is exchanged and then the information stored in the ECM memory is compared with the transmitted code from the diagnostic tool. One of the main verification steps is to compare the data of the VIN-code of the car, which is individual for each car.
Diagnosis of malfunctions of the EPBZD system
In the same way as when checking for the presence of ECM error codes, the error codes of the EPBD system are detected. A diagnostic tool is connected to the diagnostic socket, after which the error codes are read.
Here are the main error codes, exemplary malfunctions and their elimination methods.
Error code DF055 - coded line circuit. Most likely, the connection between the electronic units of the EPBDD and the ECM is broken - they check the connection between the contact 40 of the EPBDD unit and the contact 58 of the ECM.
Error Code DF059 - There is no communication between the EPBD ECU and the ECM. Check the condition of the contacts and the reliability of their connections, as well as the corresponding circuits for a short circuit from +12 V or to «mass». After troubleshooting, clear the error codes from the ECM memory.