Last night at the end of my 30 min ride home from work my 2002 RX300 with 120,000 on it had the check engine light come on as well as the ASC light. Then I noticed it wasn't going into OD even if I turned it on or off. Also the D light in the gear indicator on the dash is not on. I pulled the code and it is P0768.
The trans has been fairly well maintained, I know the fluid and screen was changed at about 50K, 80K and 110K.
Any ideas what this can be? The transmission shifts fine, it just does not shift into OD. I attached a picture of the trans showing all the solenoids, anyone know which one is setting off this code?
Thanks in advance.
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It should actually be behind what you just showed, the valve body, and is related to Shift Solenoid D. I can't tell from the diagram you showed which one this would be and unfortunately I don't have the access to alldata to confirm which one would be the actual one. My uncle in Mexico used to have a disk for it and I remember that it would show the designations. If you go to a Lexus dealer to get the part, they will show in their computer which one is A, B or D. Sorry I can't help you more on this.
Lex Mex that is the exact code I had when my tranny went bad. The solenoid and the valve body were contaminated with metal debris. I tried cleaning the valve body, but the debris had done its damage. Ended up with a rebuild. I suspect the debris stops the movement of the solenoid in the valve body. I hot wired the solenoid out of the car and it worked fine, but the piston in the valve body was scored and damaged.
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To get to solenoid 4, the valve body has to be removed and when you place it on the floor with the circular opening opposite the side close to you, then the first solenoidon the right is Shift solenoid S4.
The procedure is as below but you may have to get to a shop where you can get the repair manual for the figures.
P0768: SHIFT SOLENOID S4
Shifting from 1st to overdrive is performed in combination
with on and off cycle of shift solenoids SL1 and SL2. Solenoids are
controlled by ECM. If an open or short circuit occurs in either
solenoid, ECM controls remaining shift solenoids to allow vehicle to
operate and ensures smooth transaxle shifting. See Fig. 4. ECM checks
for an open or short circuit in shift solenoid S4. DTC will set when
ECM detects solenoid is energized and resistance is 8 ohms or less, or
when solenoid is not energized and solenoid resistance is 100 k/ohms
or more. Possible causes are:
* Open or short in solenoid circuit.
* Shift solenoid malfunction.
* ECM malfunction.
Diagnosis & Repair Procedure
1) Access ECM, located behind glove compartment. Disconnect
appropriate ECM connector. Using a DVOM, check resistance between
ground and terminal S4 at ECM connector. See Figs. 9 and 10.
2) Resistance should be 11-15 ohms. If resistance is as
specified, replace ECM. If resistance is not as specified, disconnect
10-pin solenoid connector, located above PNP switch on side of
transaxle. See Fig. 1. Check circuit continuity between ECM connector
terminal S4 and solenoid connector terminal No. 8. See Fig. 7.
3) If continuity exists, check shift solenoid S4 for
malfunction. See appropriate solenoid test under COMPONENT TESTS. If
continuity does not exist, check and repair wiring harness or
connector between solenoid connector and ECM.
I have an occasional code P0768 so I found this thread.
If I understand correctly the S4 solonoid is the black connector with red wire on top left corner is the S4 (picture posted by Cam69ss)? It measure 13.3 ohm which is within 11-15 Ohm ( per RM911U)= OK.
During removal of solonoid, couple thing came out and I wasn't prepared to see where it fell out from so I need advice on what goes where (see my pic).
1- what spring color( red or white) goes in the piston?
2-Where does the black plastic with ball bearing goes? Does the small spring goes inside it as shown or it belong else where?
3-How do you pull the blue connector? bolt and holder is removed.