Failure phenomenon: a 2006 annual Shanghai GM Buick LaCrosse sedan, traveling more than 80,000 km, before customers reflect radar parking assist system does not work.
Check Analysis: I take the car test, turn the ignition switch, shift lever linked to the block D, the hand on the front bumper in front of two radar probe, the parking assistance system does not respond, described before poise assistance system does have problems.
FIG 1
before servicing I look at a circuit diagram (FIG. 1), analyze the location and cause of possible malfunctions. Since only two prior radar does not work, and the grounding unit of the power supply control would not have considered possible failure site has: P200 plug, two probes, each signal line and the signal D range, there is a control unit itself.
possible fault location is clear, it began to be checked. Look at P200 plug assembly very reliable, pin no problem. Remove from the rear windshield parking assist system control unit, unplug the front with two wires shorted probe line, measured 17 with the pins 15 and 18 and the resistance 15 with a multimeter, respectively, are 3 Omega; while measuring pin 18 and the resistance 17 to ground is infinite, indicating two lines before the probe is no problem. Then the measured voltage pin 20, the ignition switch is opened, the selection lever is outside the D range, the voltage is 10 V; D block when linked to a voltage 0 V, the position signal is not a problem. Pin plug and there is no problem, ultimately, is the control unit, replace the control unit as long as the problem is solved, who knows fitted with the new control unit failure remains. Then repair trouble.
are not thinking of the time, the customer’s word reminds the author mdash; mdash; this car has not been a problem before the repair, after completing such a way. Ask the customer to know that behind this car had knocked over after the body lines and a control unit replaced, do not spare a problem? Spare parts from the control unit to know only one, but several harness. Found that physical and circuit diagram does not match the physical more than a black line (Figure 2) in the No. 14 pin, the role of this line maintenance manual did not say when the observation harness connector Is this the root of the problem lies in the black line? Measuring the shape of this lineState, which is found to a grounding wire.
FIG. 2
Troubleshooting: this cut line, the system will return to normal in all, before the test radar also work properly, the problem is solved. Why is this so? Later, the inquiry found spare parts, LaCrosse cars with parking assistance system has two kinds, one is only Hou Leida probe, one is before and after radar probes have. The control unit is only one, how to achieve it? The original control unit 14 is a front foot radar line disabled, this pin to ground to obtain a signal after the front radar inoperative, while the fault is not reported.
(Yi name)