Case 1
Failure phenomenon: a 2008 annual output of 3.0 L LaCrosse sedan, mileage 30000 km. According to users to reflect, car interior light does not shine.
FIG 1
Check Analysis: After examination, all indoor lights are not bright. Interior light fuse check the fuse box in the dashboard, it has been unplugged, 10 A inserted immediately blown fuse. This then disconnect the fuse, the fuse pins between the ends X and Y foot pin (FIG. 1) in series with the test lamp 21 W, high lamp brightness test, indicating that there is a short circuit. In the driver’s seat, and all doors closed, find the pilot light goes out, then the two reading lights and a rear portion of the front two open reading light, the reading light can be properly illuminated, indicating that the reading light the bulbs are good, and can determine the interior light does not shine failure phenomenon occurs when you open the door, and disappear when you close the door.
FIG. 2
Now interior lamp circuit diagram (FIG. 2), a maximum output voltage is found from the vehicle body control unit 12 is foot of BCM J1-43 V variable optical power, the normally closed contact to the lamp assembly within the chamber, and then supplying power to the lamp and the ceiling interior door trim 4 lights. Because failure the door is opened, that is to say as long as the body control pin J1-43 of the output unit becomes light BCM power supply, the fuse will be blown. Reference to a circuit diagram, first disconnect the rear instrument panel fuse box P220 / C4 plug Fuse failure phenomenon disappeared, but this time the room lamp and the ceiling 4 on the door panel lights are not lit. And then disconnect the plug P390 (in the right C-pillar trim), and before disconnecting the plug P220 reinstall the door trim can see four lights can be normal lighting.
As can be seen from the above examination, it appears to be short-circuited portion or member on the line after the plug P390, i.e. indoor ceiling lamp or a line. Open the car roof, handle really found at the right in the ceiling have broken line (FIG. 3).
Figure 3
Troubleshooting: the line breakage sheath properly wrapped, again after repairTroubleshooting car.
Review Summary: This failure seems more difficult, but after correctly analyze the fault and reference schematics can be more easily resolved. If there is no circuit diagram, this failure would be more difficult to repair them.
Case 2
Failure phenomenon: a 2008 annual output of 3.0 L LaCrosse sedan, mileage 20 km. According to users to reflect, and then turn off the car driving the car not start.
check analysis: examination found that the starter is operating normally, but not the car. Measuring fuel system pressure of 420 kPa and a normal holding pressure. Battery analysis data is normal, the normal ignition performance check. Remove the spark plug check, but no significant gasoline black electrode attachment. Measuring the cylinder pressure, the cylinders were about 600 kPa (low). Refitted spark plug before starting the engine when the vehicle has signs of full throttle, sometimes the car, but the engine obviously jitter, no data misfire misfire, exhaust pungent. See data flow engine, the intake pressure of 85 kPa (high), using the vacuum gauge measuring the intake manifold vacuum of 15 kPa, and the value of the engine corresponding to the data stream, the replacement of the data after the intake pressure sensor unchanged . The engine control unit stores a fault code p0016 (crankshaft position sensor associated with the camshaft position sensor), the current can not be eliminated, the cylinder swirl test each cylinder do no leakage.
The data-flow analysis engine, the intake manifold pressure is too high, so I have suspected leak at the manifold. EVAP respectively disconnect the fuel hose and vapor recovery hose brake booster, and check the intake manifold gasket, cracking and no air leakage, thus suspected mechanical failure timing system. Removing the timing when the front cover when the inspection timing, the timing can be seen on the timing sprocket dislocation-mark, but the car engine with the variable intake phase control, the timing between the camshaft and the camshaft sprocket there camshaft phaser effector functions ligation. Remove the camshaft position sensor, crankshaft rotation observe the rotation of the camshaft, the camshaft can be found in the clockwise rotation of the crankshaft is rotated together with the crankshaft, the crankshaft through inversion about 20 deg; camshaft but no operation. Again the forward rotation of the crankshaft, camshaft adjuster actuator (FIG. 4) inside the lock pin has a similar pop sound, this time regardless of forward or reverse rotation of the crankshaft, the camshaft are functioning normally.
Figure 4
Troubleshooting: from visual inspection since no obvious abnormality was found, from the appearance can not be determined whether the timing of the camshaft adjuster has a problem, but before the examination revealed the presence of camshaft timing adjuster works abnormally, so the replacement. After replacing the camshaft actuators, measuring the cylinder pressure of 1.05 MPa, the normal vehicle starting, idling stability, no pungent odor exhaust, intake pressure sensor data as 35 kPa (normal).
Review Summary: During the inspection because the car can not start properly, so laborious data collection, which has caused great difficulties for maintenance work. Later, by the intake air pressure data analyzed to determine the direction of the inspection, the cylinder valve and excludes swirling test cylinder head gasket leaks, the point of failure will eventually locked to the timing of the camshaft adjuster. Camshaft timing adjuster no appearance failure, engine failure appeared to be adjusted due to an interior of the intake phase disorder.
(bovine head loss)