Lexus LS430 P0756

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Tomioka

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Currently diagnosing an 04 Lexus LS430 with the 6 speed A761E trans throwing codes P0756 (S2) and P0761 (S3). Pulled the connector from the ECU to check solenoid resistances. Solenoid 2 tested 80Ω. Solenoids 1,3,4 tested 15Ω which is at factory spec. Looking to replace S2 solenoid. Is there any other possible issues that could throw these codes?
 
P0756 is for S2 Solenoid "B" Mechanical Performance
P0761 is for S3 Solenoid "C" Mechanical Performance

These codes point toward a failure in.....
*The Solenoid are mechanically stuck On or Off.
*The Shift Valves that the solenoid/s control are stuck/sticky from valve body bore wear or debris.
*Worn clutch in the transmission.
*Damaged/Inoperable solenoid driver in the ECU.

The easiest way to troubleshoot the solenoids & drivers is with a Bi-directional Scan Tool & a Graphing Voltmeter/Scope......Do you have access to this equipment?

Ohm'ing the solenoids shouldn't be part of the trouble-tree/flow chart for P0756/P0761 as there are other DTC's for Solenoid High & Low Electrical Faults.

You can take a 10amp Fused jumper wire hooked to battery+......And activate S2 & S3 solenoids at the ECM connectors (ECU unplugged-Key off)......
*Listen for a audible Click.
 
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Replaced the S2 (Green) solenoid with a ROSTRA solenoid. While underneath I ohm'ed the 4 shift solenoids with S2 reading 63Ω and the rest within 11-15Ω showing that the wiring between the trans and ECU is intact.
Installed new filter and refilled with 5qts WS ATF. Checked fluid by warming it up to spec (115-130°F) and removing CHECK drain plug.
Took it for a test drive checking low speed shifting and high speed shifting and checked it for leaks after.

It's the cheapest fix before having to replace the ECU from what I read on other forums with the A761E throwing P0756 codes and the service manual wasn't much help either. OE solenoids were difficult to find and insanely expensive and the Shipped from China superduper cheap solenoids were a no go from me dawg. Got the solenoid from a Texas ebay seller that carried aftermarket parts so that was a godsend.
Car has 192,000mi so it's not done tickin yet.
 
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