BMW 318i A/C Not Cooling

Vehicle model: 318i

Year: Dec. 2004

Engine type: L13A3

VIN: LBVEY97044SA41816

Fault phenomenon:

When turning on the air conditioner during driving, the air conditioner is blowing hot air. And it seems that the compressor does not function. The instrument displays that the outside temperature is -40 degrees (See Figure 2). The Air conditioner does not cooling.

Fault diagnosis and analysis:

The vehicle, with electronic control system, has self-diagnosis function. You need to perform the following test according to the instructions below with Fcar diagnostic scanner.

1. Find the location of diagnostic socket (See Figure 3);

2. Connect OBD test head and the main unit with test lines respectively;

3. Connect the diagnostic socket, and turn ignition switch to ON position;

4. Turn on the power of Fcar diagnostic scanner;

5. Enter the menu and select [EUROPE] - [BWM] - [V7.7] - [3 series] - [3’_E90/E91/E92/E93(2004~)] - [Body] - [IHKA integrated automatic heating/air conditioning] - [Read DTC] - [ CE outside temperature sensor] - [Clear DTC] - [DTC is cleared successfully] – [Read DTC] – [System is OK] – [The instrument still displays -40 degrees] – [Turn OFF ignition key] – click [Read DTC] – [ CE outside temperature sensor] occurs again.

It was caused by damage of outside temperature sensor and circuit fault, analyzing according to the DTCs read. The main functions is to check the outside temperature, measure the temperature difference between inside temperature and outside temperature, defrost when it is cold, and control cooling system of air conditioner. After learning about the functions of outside temperature sensor, perform the inspection of outside temperature sensor as follows:

1. Remove outside temperature sensor and heat it with warm water to see if there is any change of thermometer on the instrument.

2. Measure whether the utilization voltage is between 5V——4.1V with multimeter, and check if supply lines communicate properly.

Attention: Power must be OFF when connecting or unplugging the sensors and ECU. Otherwise, electronic control system might be damaged by current produced!

 

3. Measure whether the resistance is normal with multimeter, between 3.6MΩ and 6.8MΩ. Resistance value varies with the climate. Thus the resistance measured might be different.

4. Under the circumstances of no sensor, a resistance between 3.6MΩ and 6.8MΩ can be used to replace outside temperature sensor temporarily according to the climate, in order to repair the vehicle as soon as possible. This operation must be performed by a specialized person. Otherwise, the electric equipment might be damaged.

Troubleshooting:

Figure 4 Location of outside temperature sensor

Outside temperature sensor

Replace outside temperature sensor (See Figure 4), and clear DTC with FCAR diagnostic scanner. It displays that the DTC is cleared successfully. The system is OK. Start the engine and turn on the air conditioning system. The instrument displays that the outside temperature is 27 degrees. The trouble is solved.

Replacing engine computer board operation methods

Computer does not record the current matched injector coding (computer board doesn’t save currently installed on the engine), can lead to abnormal engine fuel consumption, engine power reduction, the injector code must be written into the engine computer board, so that let computer board have proper fuel supply according to operating state of engine total system.

Operation Methods: (all engine control system components are connected properly, the vehicle ignition switch in the ON, the engine is not running)

A: Fcar car scanner connect with vehicle diagnostic socket;

B: Turn on Fcar main unit switch to switch on main unit, select the diagnostic menu;

C: According to current maintenance models, select models on menu successively - the engine model, enter;

D: After enter system first choose[read DTC] and according to content of fault code to make the appropriate treatment. After treatment select [Clear DTC] to ensure system no fault code;

E: Select the menu [Write QR Code];

F: Follow the prompts to write the corresponding fuel injector code for each cylinder and confirm to save.

Note: If replacement of the computer version, injector QR Code can be viewed on the injector, the injector code is composed of numbers and letters. If the old PC version can enter system and read injector code while the fuel injector not replaced, can select the [read QR code] menu after entry to system, print and save the QR code of each cylinder read. After installed a new PC version, you can input respectively, note the code inputted of each cylinder need to match with the actual, mismatch can cause increase of engine fuel consumption or decrease of engine power.

About pin definition of Euro III and Euro IV vehicle engine diagnostic socket

Normally diesel vehicle is 24 V battery voltage. So here take 24V as an example, make a brief introduction about pin definition of Euro III and Euro IV vehicle engine diagnostic socket.

1. Euro III vehicle 

This vehicles usually adopts KWP2000 communication protocol, diagnostic socket is usually 4-pin.Convertion is ground wire, fire wire, K line 1,kK line 2.Use high resistance type digital multimeter under the condition of ignition key on.（Here will not introduce how to use multimeter）,measure the voltage of 4 pins respectively, normally ground wire 0V,fire wire 24V,2 K lines are about 22V(little lower than voltage of fire wire).

Now connect one end of main testing cable to car diagnostic code reader, another end DB15 connect to jumper box. Select the correct jumper according to pin on vehicle, connect ground wire on vehicle to GND on jumper box, fire wire to VCC. 2 K line connect to 7# and 15# jack respectively. Now Power light on jumper box will be seen on, and then select the correct vehicle model menu in automotive diagnostic scanners to enter. If still unable to test, you can contact Overseas Dept. of our company for assisting test.

2. Euro IV model 

This model usually adotps CAN communication protocol (Not excluding some Euro IV vehicles that still adopts Euro III standard, Such as FUSO) Diagnostic socket is normally 4 pins: ground wire, fire wire, CAN_H, CAN_L, voltage measured is: 0V, 24V, 2.5+V, 2.5-V.The pin that little higher than 2.5V

Node relation of jumper box is:

1#：K line； 2#：K line；

3#：K line； GND：Ground wire（negative）；

6#：CAN‐H；

7#：RSR232+, J1708+, K line；8#：K line；

9#：K line； 10#：K line；

11#：K line； 12#：K line；

13#：K line； 14#：CAN‐L；

15#：RSR232‐, K line, J1708‐, L line

VCC: power line（Positive）； POWER：Power indicator.

Remark: If lack of vehicle electrical equipment knowledge or unable to confirm electrical equipment power supply, please don’t operate jumper, for error operation of jumper may lead to malfunction of electrical failure or FCAR F3-D main unit and wire. 

(Auto diagnostic socket related information reconfirmed as below)

● Digital high impedance multimeter (can not use Analog Multimeter)

● When ignition switch to ON Gear, there is supply voltage of vehicle on diagnostic socket. Voltage difference between voltage on diagnostic socket and vehicle battery side can not be above 2.5V.

In diagnosis, if the signal line used is single-line communication (K line), voltage on signal line lower than battery voltage,(if vehicle supply voltage is 12V,then voltage on signal line is 11V, + 0.25V;if 24V,signal voltage is 21V,+ 0.25V)

If double signal line adopts CAN communication, 2 diagnostic lines use multimeter to measure ground wire voltage under the condition that ignition switch open, the sum of both voltages is 5V,average 2.5V,the one voltage little higher than 2.5V is CAN-H, the one voltage lower than 2.5V is CAN-L.

After understanding of the above, then you can use car diagnostic scanners to read DTC. Now make a brief introduction of operation steps for FCAR auto scanner to read DTC: Confirm diagnostic socket connect properly and then turn on power switch of auto scanner, and select Diagnostic menu.

How to use auto diagnostic scanners to analyze engine and other components fault

FCAR - Today's car is a very advanced machine. Long gone are the days when your mechanic would take the whole day inspecting the engine and other components in order to diagnose the vehicle's fault. With the installation of the car computer on most vehicles, diagnoses have become simpler and faster.

Most vehicles manufactured between 1992 and 1995 have an On Board Diagnostics I (OBD I) facility while those manufactured after 1996 have the OBD II. OBDs are defined as the electronic systems installed in cars to help in regulating and optimizing engine performance. This system however needs an auto diagnostic tool for the car owner or mechanic to be able to analyse the fault the car is experiencing.

So how does the automotive scan tools work? And how to use auto diagnostic scanners to analyze fault,the following will tell you.

Fault Analysis auto diagnostic scanner

To analyze according to reading data stream, the vehicle engine still cold water temperature sensor data stream is 95 degrees, the intake pressure sensor data 120kPa. Start the engine, after idle for some time no change in water temperature data, depresses the accelerator pedal to increase engine speed, view the data stream, intake air pressure sensor data is still 120kpa unchanged, indicating that the water temperature sensor and intake air pressure sensor data is abnormal (see data stream of this vehicle in Table 2, Table 3 are data stream that has some changes), initially judge water temperature sensor and intake air pressure sensor part is defective.

Check water temperature sensor and intake air pressure sensor, both of which were found abnormal, to be replaced.

Troubleshooting

Replace water temperature sensor see Pic.2,inlet pressure sensor see Pic.3. Use menu on Fcar auto diagnostic scanners menu to clear DTC ,display clear success,Read DTC, system normal,road test,fault disappear,completely remove fault.