Testing sequence to confirm a bad Engine computer(ECU).
The ECU of an automobile is one the most protected component(Module) in the vehicle,
it is designed to withstand and shutdown(Go into Limp mode or Fail safe mode) when there is a voltage surge within its related circuits, its a very fragile component that requires careful handling, about 80% of the engine computers(ECU) being replaced are in good working condition.
Before recommending replacement ensure that the underlisted test sequence is carried out.
A low or non avaliabilty of 5v reference voltage on all the critical sensors implies that you have a bad engine computer(ECU).
A circuit integrity test on the circuitry of the critical sensors is required to narrow down, if the engine computer(ECU) is bad.
The critical sensors are the five(5) or more sensors that depends on the engine computer(ECU) for 5v reference voltage or ground control for there functionality
A short to ground in any of the the cirtical sensor circuit can lead to a shutdown or Pulldown(Go into Limp mode or Fail safe mode) of engine computer(ECU), Which will
in turn affect the functionality of these sensors and the vehicle, this does not imply that the engine computer(EUC) is bad.
Fault Codes Associated with a bad Engine computer(ECU)
If we understand our fault code designation very well, the Computer systems/communication fault codes(PX6XX) has to do with the computer communications,
implication is that once an extracted fault code bears these type on nomenclature it tells you check if Engine computer(ECU) has being compromised.
Fault codes from P0601 to P0610 tells us to careful check the engine computer(ECU) taking all specified test into consideration.
Another set of fault codes that can deceive us to think that the engine computer(ECU) is bad are the Network communication fault codes (UXXXX), to avoid any deception fix the issues related to the UXXXX fault codes before any other fault code
Tools required
1. Multimeter
2. Relay tester
3. Test light
4. Electrical wiring diagram
Testing requirements
1. Basic understanding of Ohms law
2. Indept understanding of the multimeter useage
3. Indept understanding of electrical wiring diagram reading
Test Sequence
1. Check the related fuses and relays for continuity and switching power respectively
2. Check for 5v reference voltage and good ground on the critical sensors
3. At KOEO disconnect the critical sensors one after the other, while your multimeter in voltage measurement is connected to one of the sensor feed wires, if the measured voltage increases to 5v volts when a particular critical sensor is disconnected, that should be the sensor with the faulty circuit.
4. For components that are difficult to reach, check for circuit resistance(1k ohms or more is ok) by back probing on the specified ECU connector.
Test validations
1. Engine computer(ECU) is good if most of the critical sensors have good ground or 5v reference voltage.
2. Engine computer(ECU) is bad if all the critical sensors lack good ground and 5v reference voltage
3. Engine computer(ECU) is good if the there is good communication with the scan tool
4. Non illumination of the check light does not neccessry mean bad engine computer(ECU)
Causes of Engine Computer(ECU) damage
1. Voltage overload(caused by short in a solenoid, actuator circuit or any of the critical sensor circuit if not located and fixed)
2. Envviromental factor(corrosion, thermal stress or vibration)
Dont just replace that engine computer(ECU) or any malfunctioning/failing component,
Fix the problem by narrowing down to the cause of the component malfunction/failure….
THINK FIRST and LOOSE AFTERWARDS
