Car mileage over 300,000 km, configuration V6 engine and 4T65 E -type automatic transmission models 2001 Shanghai GM Buick GL8 commercial vehicle . Users report: weak obd2 acceleration when driving the car when the engine reaches 3500r/min, but super speed 120km / h, engine failure lights .
After receiving the car : power systems for self-diagnosis , there is a fault code P0752, file contents 1-2 shift solenoid valve failure , or 4th gear without a gear . Clear DTCs, road test , the fault persists . View 1-2 shift solenoid valve work file data, no short circuit or open circuit fault information .
The automatic transmission shift solenoid valve configured with two 1-2 / 3-4 shift solenoid valve ( 1-2 gear shift solenoid valves ) and 2-3 gear shift solenoid valves. This is the same structure as the two solenoid valves are normally open solenoid valve , which in case of power failure (Off) Road case oil solenoid valve opens , slot board / body oil passage communicating with them in an open state ( state relief ) . In the solenoid valve is energized (0n) case , the internal oil passage electromagnetic valve is closed, the groove board / oil passage communicating with the valve in the closed state ( hydraulic established ) , a time to control the operation of the shift valve spool .
If the file 1-2/3-4 shift solenoid valve fails, the only two forward gears and 3rd gear , vehicles rose less than 4 files. Combined with previous experience in the analysis , consider the following possible faults 1-2 gear shift oil duct blockage , 1-2 / 3-4 shift solenoid valve catching 1-2 shift spool file catching 1 – 2/3-4 gear shift solenoid valve leakage , Car Diagnostic Software automatic transmission fluid is too dirty and so on. Replace automatic transmission oil , failure is not ruled out. Remove the automatic transmission side cover , check the slot board / body, outside no problem. Remove files 1-2/3-4 shift solenoid valve , measure resistance, as 25Ω, within the standard range . The 1-2/3-4 shift solenoid valve to replace the lost files , test, failure to completely ruled out.
When the PCM commands the solenoid valve is closed , does not provide grounding circuit and the input to the line pressure solenoid valve is vented through a filter . When the PCM commands the solenoid valve is turned on, providing Ground loops and blocked the exhaust port , stop the discharge pressure of the gas pipeline . PCM gear by monitoring the commanded gear ratio and the relation of Claim 1-2 shift solenoid valve (1-2SS valve) position . If a PCM file when the instruction is detected and the detected gear speed gear 2 , and the fourth speed gear when the instruction is detected while the third speed drive gear ratio , set a fault code P0751.
When 1-2/3-4 shift gear stuck in the off position solenoid valve , automatic transmission only 2nd and 3rd gear , the vehicle accelerates weakness. Power system control unit bad 1-2/3-4 shift solenoid valve performance file , set the fault code P0752, engine fault light is lit , fault protection mode is enabled , the automatic transmission in third gear lock operation by calculating the ratio judgment.