The total repair cost will vary based on the condition of your vehicle and the number of repairs needed to fix your symptom. Proper diagnosis will save you money by finding the exact repairs needed to fix your car right the first time.
When the throttle position sensor fails, the engine's computer tends to overcompensate with fuel, leading black exhaust coming from the tailpipe. There is a strong possibility of engine misfires, and the check engine light will come on.
Throttle position sensors can also develop "dead spots," or certain places along the throttle curve where it doesn't get a reading. When this happens, the above symptoms can occur but then stop when you further press or let off the gas pedal.
When the vehicle speed sensor fails or the wiring harness prevents signal transmission, the speedometer is the first thing that will stop functioning properly. This can be an intermittent issue where the speedometer only works occasionally, the speedometer may cease all function, or the speedometer may read erratically or incorrectly. Also, the traction control and anti lock brake warning lights specific to each vehicle may be illuminated, depending on the design of those systems. You may notice the vehicle hesitate to accelerate, cruise control will not function properly, and the vehicle may not shift properly through all of the gears.
In the event that a wheel speed sensor fails, the ABS, traction control system (TCS) and manufacturer specific stability control system lights will illuminate, informing the driver that the systems are disabled. The vehicle will be more prone to tire slip, and normal driving patterns may need to be adjusted to correct for the loss of computer control. On older vehicle's, the speedometer can be affected, causing illumination of the check engine light as well.
The cruise control switch can cause complete failure of the cruise control feature, but in a lucky scenario only partial functionality will be lost. This means that the cruise control may come on, but that it will not increase in speed automatically, or the cancel button does not work leading the driver to cancel cruise control with the foot brake. In some vehicles, the cruise control light may illuminate, or a warning message may be displayed due to lack of functionality.
To effectively diagnose a non-functioning cruise control in your 1993 BMW 740i, start by examining the wiring diagrams and the clock spring connection, as these are crucial for the steering wheel controls to function properly. Next, ensure that the brake lever is fully returned and that the brake lights are not illuminated, as these conditions can inhibit cruise control engagement. If these initial checks do not resolve the issue, inspect the cruise control unit for any signs of damage, particularly dried out electrolytic capacitors, which may need replacement to restore functionality. Additionally, verify that the cruise control buttons are receiving the correct signals by checking the associated block or the engine controller's measurement block. If the cruise control still does not activate, try pressing the Cruise On and Set buttons simultaneously while the Cruise Off is engaged, as this can sometimes reset the system. Should you encounter specific error messages like "ACC is unavailable," it may indicate sensor misalignment, which requires further troubleshooting. If these steps do not yield results, it may be wise to consult a qualified BMW technician, especially if the Engine Control Unit indicates potential issues such as low transmission fluid or a failing alternator, to prevent further complications. By following this structured approach, you can systematically identify and address the issues affecting your cruise control system.
When troubleshooting cruise control issues in a 1993 BMW 740i, it's essential to consider several common problems that could be at play. One frequent culprit is a faulty vehicle speed sensor, which can disrupt the system's ability to maintain speed. Additionally, electrical issues or a malfunctioning instrument cluster may lead to unreliable cruise control performance. Another common issue is the rear brake light switch failure; if this switch is not functioning correctly, it can prevent the cruise control from engaging. For those with adaptive cruise control, it's worth checking the vehicle's settings, as disabling this feature can sometimes restore normal functionality. Furthermore, problems with the steering angle sensor or control module, as well as low power steering fluid levels, can also impact the cruise control operation. Lastly, high-mileage models like the BMW 740i may experience issues related to air suspension systems, particularly with rear height level sensors or air springs. By systematically diagnosing these potential problems, DIYers can effectively address the root causes and restore their cruise control system to proper working order.
Repairing the non-functioning cruise control in your 1993 BMW 740i is not just a matter of convenience; it is a critical safety concern that should be addressed without delay. An illuminated Check Engine Light (CEL) accompanying the cruise control malfunction often signals underlying issues with the speedometer or the cruise control system itself, which can escalate if left unattended. Ignoring these symptoms can lead to more severe problems, potentially compromising the vehicle's performance and safety. Moreover, a functioning cruise control system enhances driving comfort, particularly on long journeys, by allowing for consistent speed and reducing driver fatigue. Identifying the root cause of the malfunction is essential, as various factors, such as faulty switches, can disrupt the system's functionality. Regular maintenance and prompt repairs not only ensure the cruise control operates effectively but also contribute to the overall safety and reliability of your vehicle on the road. Therefore, addressing the cruise control issue promptly is crucial for maintaining both the efficiency and safety of your BMW 740i.
See what others are asking about their BMW 740i. Get answers from RepairPal's community of auto experts and enthusiasts.
Read about related problems experienced by other BMW 740i drivers like you.
