Failure phenomenon: a 2003 Buick Regal with an annual output of 3.0 L sedan, traveling more than 250,000 km, the car engine burning oil phenomenon occurs, I stood in the overhaul, after completing the car lights ABS and TRAC found lights lit.
Check Analysis: fault diagnostic use reading it into the ABS control unit fault code, found stored fault code 3, respectively: C1254mdash; mdash; closing abnormality detection, C1277mdash; mdash; request torque signal circuit function failure, and C1298mdash; mdash; powertrain control unit class2 serial data connection ineffective. These three fault codes are current fault, use a scan tool can not be cleared. The author then check the engine control unit, fault code U1040 found, meaning: the electronic brake control unit and loss of communication. After entering the control unit and the other has the same fault found code.
Based on previous experience, ABS control unit can be accessed by the scan tool, the control unit declaration signal lines, power lines and grounding line should be no problem, but the control unit and the other loss of communication therewith, I believe that is probably the largest ABS control unit itself is a problem. And this vehicle ABS control unit price of 5,000 yuan, relatively expensive.
As the car such problems do not occur when pitted overhaul, but overhaul after a failure, so I asked maintenance technicians responsible for the car, its operation when disconnected from the ABS control unit is standard, and the answer is very positive, it ruled out the possibility of human error.
due to a fault code C1254 and C1298 are rare in the daily maintenance process, in order to determine the real cause of the failure, the author access to the maintenance manual instructions regarding the failure of these two fault codes. Wherein, on C1254 fault description is: when the electronic brake control unit starts the relay (open), the solenoid and brake motor. This fault code indicates a fault is detected in the battery is disconnected and the electronic brake control unit loose battery connection or ground, or when driving function failure. C1298 fault description is: class 2 control unit allows all serial data on line send one another as needed. Each control unit is assignedThe identification number, information on all lines are equipped with receiving priority. When the ignition switch is on ldquo; ON rdquo; when (ON) position, each control unit will begin sending and receiving information. Each class 2 control unit knows the serial data path information to be transmitted and received. However, which control unit may send information is unknown to them. Only after the control unit receives the information it needs, and the control unit transmits the identification number of the information, to get the information. Thereafter, the fault is memorized until the ignition switch is turned off.
I understand the meaning of these two fault code after the diagnosis process on the maintenance manual were analyzed and found these two diagnostic procedures for fault code essentially the same, are the first to check the grounding and power supply If there is no problem replace the ABS control unit. However, it is possible to use the fault diagnostic control unit detects, I believe that the power supply to ground and there is no problem. In order to confirm their own views, we decided to line the ABS control unit to be checked. First disconnect negative battery cable, then remove the plug ABS, connect the battery negative line, this time measuring the author blocking plug with an electrical multimeter grounding line, and the resistance between the negative electrode of the battery 17 Omega ;. And measuring the test lamp power cord plug, when the vehicle body Ground test lights, but with the plug Ground Ground line test light is not bright, problems do exist in the ABS control unit to ground? They then removed the air cleaner housing and remove the ABS control unit Ground line found dirty grounding point corrosion. The original fault is because ABS control unit grounding line due to poor contact.
Troubleshooting: carried out with sandpaper and the grounding point and the grounding line installed properly handled, measured with a test lamp power and grounding plug normal, measured with a multimeter plug and negative battery Ground line the resistance value between 0.5 Omega ;. After all components refitted, turn the ignition switch, ABS lights out, a read fault codes are historic diagnostic fault, the fault code is cleared after the usual work vehicle. I think the matter through experience unreliable in modern repair process, only the scientific method of diagnosis is the magic solution to the problem.
(Yong Kang East)