A/T Controls - DTC P0756 Diagnostic Tips
Information IB06-05-S004Diagnostic Tips For Automatic Transmission DTC P0756
(This Bulletin Supersedes IB05-05-S013)
ISSUE DATE: MARCH 22, 2006
Affected Vehicles
^ 2003-2007 Isuzu Ascender (US/UT)
^ 2006-2007 Isuzu i-280/i-350 (TI) with Automatic Transmission
Service Information
This bulletin is being updated to add the 2007 model years and to update and add additional service information.
Some technicians may have difficulty diagnosing DTC P0756, 2-3 Shift Valve Performance on 4L60-E automatic transmissions. As detailed in the Service Manual, when the PCM detects a 4-3-3-4 shift pattern, DTC P0756 will set. Some customers may also describe a condition of a second, third or fourth gear start that may have the same causes but has not set this DTC yet.
Below are some tips when diagnosing this DTC:
Refer to the Service Manual when diagnosing the following DTC tips:
^ This is a performance code. This means that a mechanical malfunction exists.
^ This code is not set by electrical issues such as a damaged wiring harness or poor electrical connections. Electrical problems could cause a DTC P0758, P0787, or P0788 to set.
^ The most likely cause is chips/debris plugging the filtered AFL oil at orifice # 29 on the top of the spacer plate (48). This is a very small hole and is easily plugged by a small amount of debris. It is important to remove the spacer plate and inspect orifice # 29 and the immediate area for the presence of chips/debris. Also, the transmission case passage directly above this orifice and the valve body passage directly below should be inspected and cleaned of any chips/debris.
^ This code could be set by a 2-3 shift solenoid (367B) if it were cracked, broken or leaking. Refer to Shift Solenoid Leak Test in the appropriate Service Manual for the leak test procedure. Based on parts return findings, a damaged or leaking shift solenoid is the least likely cause of this condition. Simply replacing a shift solenoid will not correct this condition unless the solenoid has been found to be cracked, broken or leaking.
^ This code could be set if the 2-3 shift valve (368) were stuck or hung-up in its bore. Inspect the 2-3 shift valve (368) and the 2-3 shuttle valve (369) for free movement or damage and clean the valves, the bore and the valve body passages.
NOTE:
It is important to refer to the appropriate Service Manual for further possible causes of this condition. Refer to Valve Body in the Service Manual to properly evaluate numbers referenced above.
Disclaimer