No pwr steering assist turning left only @ idle/low speeds

check the sensor on top of the steering rack ,their is a sensor that increases the idle when the steering is turned when the vehicle is stationary

Circuit/System Description
The assist step control module (ASC) controls the running board actuators to extend or retract the running boards. Each actuator consists of an electric motor and a potentiometer. The module supplies a low reference and 10-volt reference source voltage to the potentiometer. The ASC control module monitors the voltage drop across the potentiometer on the position signal circuit. When the actuator shaft rotates, the voltage on the position signal circuit changes. The ASC control module supplies the actuator motor with a 12-volt control circuit and a ground control circuit. The ASC module controls the direction of the actuator by changing the polarity of the control circuits.
You should take this to a ASE certified repair shop that has the diagnostic tools to check for stored DTC'S in the running board control module . A code reader for check engine light codes will not work for this system !
This system can set numerous DTC'S
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Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors
DTC B051A 0B: Left Side Assist Step Motor Control Circuit Current Above Threshold

DTC B051A 01: Left Side Assist Step Motor Control Circuit Short to Battery

DTC B051A 02: Left Side Assist Step Motor Control Circuit Short to Ground

DTC B051A 04: Left Side Assist Step Motor Control Circuit Open Circuit

DTC B051B 0B: Right Side Assist Step Motor Control Circuit Current Above Threshold

DTC B051B 01: Right Side Assist Step Motor Control Circuit Short to Battery

DTC B051B 02: Right Side Assist Step Motor Control Circuit Short to Ground

DTC B051B 04: Right Side Assist Step Motor Control Circuit Open Circuit

DTC B051C 01: 10 V Reference Circuit Short to Battery

DTC B051C 02: 10 V Reference Circuit Short to Ground

DTC B051C 2A: Left Side Assist Step Position Sensor Circuit Too Many Pulses

DTC B051C 22: Left Side Assist Step Position Sensor Circuit Low Time < Minimum

DTC B051C 29: Left Side Assist Step Position Sensor Circuit Too Few Pulses

DTC B051C 62: Left Side Assist Step Position Sensor Circuit Actuator Stuck Open

DTC B051C 63: Left Side Assist Step Position Sensor Circuit Actuator Stuck Closed

DTC B051D 2A: Right Side Assist Step Position Sensor Circuit Too Many Pulses

DTC B051D 22: Right Side Assist Step Position Sensor Circuit Low Time < Minimum

DTC B051D 29: Right Side Assist Step Position Sensor Circuit Too Few Pulses

DTC B051D 62: Right Side Assist Step Position Sensor Circuit Actuator Stuck Open

DTC B051D 63: Right Side Assist Step Position Sensor Circuit Actuator Stuck Closed
If you don't know how the system works you could make it worst !
You

Hello, This could be an indication your A/C is low on Freon or your Power Steering pump is low on fluid. Both systems are made to increase the idle speed to make the system work better. What happens in the case of the A/C, is the A/C compressor puts a strain on the motor when it engages the electric clutch on the compressor.

The A/C is wired such that when the compressor clutch engages, the engine RPM is increased to maintain the idle speed. The controls do this automatically and when your compressor is low of Freon, there is little resistance and the engine overspeeds. You are burning up your compressor if you lose the lubricant packaged inside it. That noise you hear is a dry compressor.

Turn your A/C or Defroster off and see if the overspeed and the noise stop. The compressor will run in the Defrost cycle too! Eventually your A/C will lose more of the Freon until the low pressure switch cuts the power to the compressor completely.

Some front wheel drive cars have a boost sensor in the power steering assembly for increasing the idle speed when you are turning the steering at low speeds. If the fluid level is low, it tricks the sensor into speeding up the idle to assist steering. Like in the A/C example, you can get overspeed when the fluid levels are low.

I hope my solution is very helpful in fixing your problem. Have your Freon checked or throw in an "OIL Charge" with the proper type of oil for your compressor. Then check your Power steering.

scale 1 to 10 about a 6 but make sure its not the wheel bearins cause they can houl like the axles are bad and mush easyer to change

2004 chevy tahoe 4x4 had the same problem wont turn right at idle - like no power steering , has hydoboost brake steering system , did test and found steering box bad , removed box and remove the top cover on box 4 bolts at hydralic cover and removed and found spool valve has 4 seals 1 outer was blown i replaced box with reman from advance auto about $200.00 and flushed system , drove great problem solved .

The trucks like yours have a rack and pinion steering, and when rack and pinion steering need replacing they get hard to turn in one direction just as you have described.

Check the front wheel bearing assembleys.

The steering wheel position, wheel speed sensors, and ABS systems are all used to provide traction control. You likely have a failure of one or more systems. Scan the ABS system and it will provide codes to help the diagnosis. Wheel speed sensors fail often, and it is likely one or more of these is contributing to the problem.

In some cases where the oil is not changed properly, the oil pump screen maybe plugging or your oil filter is defective. Fram is a good filter. If there is no problem found, replace the pressure sensor.

If your steering is easier above idle the problem is the pump.