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Q: Shifts early jerks engine - 1994 GMC K2500

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My truck has 235,500 miles on it. The 4x4 wasn’t working, so I replaced the actuator and that helped. I replaced the pins and bushings in the doors and fixed the window track. But I am getting a Diagnostic Trouble Codes 28 and 32. The 32 code is for an Exhaust Gas Recirculation problem. The 28 is for a quad driver module that I don’t know anything about it. My truck shifts early sometimes jerking the engine, and it will only shift into drive periodically. Some people tell me to replace the computer and some say to replace parts in the transmission. My plug is good in the transmission with No leaks. I used a SOLUS scan tool to check the codes, so I am very sure of my problems. Can you help me figure this out, and give me some ideas on how to fix this?

Hello. You will need to remove the EGR valve to clean out the carbon and then decarbonize the engine. The code 28 may be due to the transmission or transmission module controller PCM has a bad internal driver to control the transmission shifting is in failure mode. Have the engine and transmission grounds checked to the see if they are loose or corroded. If you would like to have this looked at, a certified technician from YourMechanic can come to the site of the car to diagnose the shifting issue and let you know what needs to be repaired.

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