My 2007 Z51 sevice vehicle soon light comes on randomly and i loose my speed sensitive steering i beleive and it is very hard to turn at low speeds. I have taken it to the dealer and when they plug it in they say there is no codes that come up and the sevice light goes off. It will usually turn on half way through the day when i drive it and turns off when i garage it for the night.
What triggered this to start was my powere brake cable broke and this light came on in the same day. I have gotten the brake cable fixed however this propblem persists. Please someone help i have been to two dealers and have no luck so far.

 

If possible could someone post how the speed sensitive power steering works. I have an 09 with what I suspect is having an issue with this feature. Understanding theory of operation would be a good starting point for anyone with questions about it.

 

Yes this would help or where this sensor is located so i can try to clean or replace it.

 

Service Information

2008 Chevrolet Corvette | Corvette (VIN Y) Service Manual | Steering | Power Steering | Description and Operation | Document ID: 781440


Variable Effort Steering System Description and Operation
The Variable Effort Steering (VES) system, or MAGNASTEER II® varies the amount of effort required to steer the vehicle as vehicle speed changes or lateral acceleration occurs. At low speeds, the system provides minimal steering effort for easy turning and parking maneuvers. At high speeds, the system provides firmer steering (road feel) and directional stability. When the system senses lateral acceleration, steering becomes firmer to reduce oversteering. The Electronic Brake Control Module (EBCM) controls a bi-directional magnetic rotary actuator located in the steering rack and pinion. The EBCM varies the steering assist by adjusting the current flow through the actuator. The actuator adjusts the amount of power steering assist to achieve a given level of effort to steer the vehicle. The VES system accomplishes this by adding or subtracting torque on the input shaft to the rack and pinion. The main component of the system is an electromagnetic actuator, which consists of a multiple-pole ring-style permanent magnet, a pole piece, and an electromagnetic coil assembly. The VES system uses the Antilock Brake System (ABS) wheel speed sensor inputs to determine vehicle speed. When the EBCM senses vehicle speed, it commands a current to the actuator that is most appropriate for each speed. The system also uses inputs such as Handwheel position, wheelbase, understeer coefficient and steering ratio to calculate lateral acceleration. The EBCM commands current from negative two amps to positive three amps to the actuator, which is polarized. At low speeds, a negative current is commanded, which assists steering. At medium speeds, no current is commanded and steering is assisted by hydraulics only. At high speeds, a positive current is commanded, which creates steering resistance. Ignition voltage and ground are provided through the EBCM. The EBCM has the ability to detect malfunctions in the actuator or the circuitry to the actuator. Any malfunctions detected will cause the system to ramp to zero amps and steering will be assisted by hydraulics only.



Bill

 

So what would be a starting point to fix the problem?

 

Explain this, as maybe its related. was this up front near the power steering?

 

Since it is unlikely you can read the EBCM diagnostic codes without going to the dealer you may want to assume you have the following code and follow the diagnostic procedure for it.
DTC C0450
Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC C0450: Steering Assist Control Solenoid/Motor/Actuator Circuit
Circuit/System Description

The variable effort steering (VES) system uses the electronic brake control module (EBCM) to control current to a bi-directional electromagnetic rotary actuator. The EBCM commands current from negative 3 amps to positive 3 amps to the actuator. At low speeds, less than approximately 24 km/h (15 mph), negative three amps of current is commanded, providing maximum assist to steering. As speed increases, increased (more positive) current is commanded, reaching zero amps at approximately 96 km/h (60 mph). The EBCM commands positive current only during steering input at higher speeds, based on the above inputs and the vehicle calibration, which creates steering resistance.
Conditions for Running the DTC

• Ignition voltage between 10.5-17 volts
• Off state test--Initial ignition ON, no engine RPM or vehicle speed present.
• On state test--If off state test passes, engine RPM and vehicle speed present.

The EBCM detects an open, short to ground, or short to voltage in the VES actuator or the actuator circuits.
Action Taken When the DTC Sets

• DTC C0450 is stored in memory.
• The driver information center (DIC) displays the SERVICE STEERING SYSTEM warning message.
• The VES system is disabled for the remainder of the ignition cycle.

• Conditions for Clearing the DTC
• The condition for setting the DTC is no longer present.
• The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

The vehicle may need to be driven to view full VES Actuator Commanded and Actuator Feedback Data parameters.
Reference Information

Schematic Reference

Power Steering Schematics
Connector End View Reference

Component Connector End Views
Description and Operation

Variable Effort Steering System Description and Operation
Electrical Information Reference

Testing for Intermittent Conditions and Poor Connections


Circuit Testing

Scan Tool Reference

Control Module References
Circuit/System Testing

1. Ignition OFF, disconnect the VES actuator harness connector.
2. Measure for 0 volts between the variable effort steering actuator supply voltage circuit terminal A and ground.⇒
   If the voltage is greater than the specified range, test the variable effort steering actuator supply voltage circuit for short to voltage. If the circuit tests normal, replace the EBCM.
   
3. Ignition ON, measure for 12 volts between the variable effort steering actuator supply voltage circuit terminal A and ground.
   ⇒
   If the voltage is less than the specified range, test the variable effort steering actuator supply voltage circuit for short to ground or open/high resistance. If the circuit tests normal, replace the EBCM.
   
4. Connect a test lamp between the variable effort steering actuator supply voltage circuit terminal A and the variable effort steering actuator control circuit terminal B at the VES actuator harness connector.
5. Using a scan tool, command the VES actuator ON. Verify the test lamp illuminates.⇒
   If the test lamp does not illuminate, test the variable effort steering actuator control circuit for open/high resistance. If the circuit tests normal, replace the EBCM.
   
6. If all circuits test normal, test or replace the VES actuator.

Component Testing

1. Ignition OFF, disconnect the VES actuator harness connector.
2. Measure for 5-10 ohms of resistance between the VES actuator terminals A and B.⇒
   If the resistance is outside the specified range, replace the VES actuator.
   
3. Measure for infinite ohms of resistance between each VES actuator terminal and the VES actuator housing.

If less than the specified range, replace the VES actuator.



Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• Control Module References for EBCM replacement, setup, and programming
• Steering Gear Replacement

VES connector on Steering Rack Info:
Variable Effort Steering Actuator




Connector Part Information

OEM: 12186685
Service: 12102747
Description: 2-Way F Metri-Pack 150 Series (BK)
Terminal Part Information

Terminal/Tray: 12048074/2
Core/Insulation Crimp: 2/1
Release Tool/Test Probe: 12094429/J-35616-2A (GY)


Pin

Wire

Circuit

Function

A
1 WH
1294
Variable Effort Steering Actuator Supply Voltage
B
1 BN
1295
Variable Effort Steering Actuator Control





Bill

 

drivinfast
the brake cable broke at the same time as this power steering problem happened within minutes of each other. I had told the dealer this because i thought the cable could have frayed a wire or hit a sensor however they were not impressed with my hypothosis and told me they would have to pull the steering column to attempt to diagnois the problem. I do not think the brake cable is near the steering column and that is what they thought.

 

Anyone else have any suggestions. Please help

 

Hopefully Bill Dearborn or others can answer

1. Where is the ECBM?

2. Where is the VES actuator? Is there anything that makes it easy to know when I have located it?