Mechanics

ENGINE

1999 Lexus RX 300 • 6 cylinder 2WD Automatic • 190,000 miles

99 RX 300: I posted this question early today but didn't have any codes. When I start up I have to keep my foot on gas, once I start driving the car****** while changing gear, once it change into all gear it runs pretty good. CEL came back on and there are 4 codes: P0758, P1760, P0171, P1133, HELP!
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Mno221
April 21, 2011.



DTC P0758: SHIFT SOLENOID SL2
Circuit Description
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, DTC will set. ECM controls remaining shift solenoids to allow vehicle to operate and ensures smooth transaxle shifting. ECM checks for an open or short circuit when solenoid is energized (duty cycle exceeds 75 percent), and when solenoid is not energized (duty cycle is less than 3 percent). Possible causes are: • Open or short in solenoid circuit.
• Shift solenoid malfunction.
• ECM malfunction.

DTC P1760: SHIFT SOLENOID SLT
Circuit Description
Throttle pressure applied to primary regulator valve, which modulates line pressure, causes shift solenoid SLT to precisely and minutely modulate and generate line pressure according to accelerator pedal effort, or engine power output detected. This reduces line pressure and provides smooth transaxle shifts. Upon receiving throttle valve opening angle signal, ECM controls line pressure by sending a predetermined duty cycle to shift solenoid SLT, modulating line pressure and generating throttle pressure. Duty cycle is ratio of period of continuity in one cycle. Shift solenoid SLT is located on transaxle valve body. DTC will set if voltage at ECM terminal SLT- is zero volts or 12 volts for one second or more. Possible causes are

• Open or short in solenoid circuit.
• Solenoid malfunction.
• ECM malfunction.

DTC P0171 : SYSTEM TOO LEAN

Circuit Description
Fuel trim refers to feedback compensation value compared against basic injection time. Fuel trim includes short-term and long-term fuel trim. If total of short term fuel trim value and long term value is within 25 percent, system is functioning properly. DTC P0171 is set when fuel trim is rich beyond a certain value. Possible causes are: • Exhaust system leak.
• Air intake hose loose.
• Fuel line pressure.
• Injector blockage.
• Faulty Mass Airflow (MAF) sensor.
• Faulty Engine Coolant Temperature (ECT) sensor.
• Faulty A/F sensor.

DTC P1133 : AIR/FUEL SENSOR CIRCUIT RESPONSE MALFUNCTION

Circuit Description
Air/Fuel (A/F) sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. ECM uses input signal to control air/fuel ratio. A/F sensor includes a heater. DTC is set when A/F sensor output does not change with engine speed at 1400 RPM or more with vehicle speed at more than 38 MPH. DTC P1133 is for bank No. 1 A/F sensor.

Possible cause is: • Faulty A/F sensor.

KHLow2008
Apr 21, 2011.
Thanks again for your response, seem like a lot going on here, any suggestion where to start first, could one be causing a domino effect.I clean the MAF and its still a lot rough when I start but I dont have to keep my foot on the gas.

Tiny
Mno221
Apr 22, 2011.
I would start with DTC P1133. If the sensor is bad, it can cause idlng and other issues.

KHLow2008
Apr 22, 2011.
Replace the sensor and it run much better. I going to change the tranny fluid and it used ATF TYPE T-IV, I was told MOBIL 1 ATF was better.

Tiny
Mno221
May 3, 2011.
Nobody does it better than the manufacturer as the recpommended fluid is specifically formulated for the transmission when it was designed.
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KHLow2008
May 3, 2011.
Ok thanks manufacturer it is.

Tiny
Mno221
May 4, 2011.
You're welcome.

Have a nice day.

KHLow2008
May 4, 2011.
Ok i'm back, I change the tranny fluid and filter, manufacturer, I change the rear diff and front transfer case used royal purple gear oil, but there is still a***** when it change gears, it dont surge and***** as before but there is still a little***** 1/2 and 2/3. If I pull off in drive 2 and get the speed up then take my foot off the gas and shift into D it dont*****. Where do I go now?

Tiny
Mno221
May 6, 2011.
Have a scan done to check if there are any trouble codes. Harsh shifting can be due to bad engine mounts but symptoms does not indicates so.

Since the trans fluid has just been replaced, run around and hope it clears up something and shifting improves.

KHLow2008
May 6, 2011.
I'll have auto zone run scan to see if there's any store codes even thou the CEL is not on.I'll get back with you. THANKS!

Tiny
Mno221
May 6, 2011.

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