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.
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.
If the cruise control refuses to turn on at all, the actuator could be at fault. Likewise, if the cruise control stays on but does not maintain a consistent speed, the problem could be a bad actuator. In extreme cases, a malfunctioning actuator could cause the throttle to stick and prevent the vehicle from slowing down. These symptoms may point to a bad actuator. They may also point to other problems with the cruise control and related systems.
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.
A faulty cruise control module will simply result in deactivation of cruise control settings. This is because a detected error in the cruise control system could lead to hazardous driving conditions, so the module will be disabled, and the cruise control system warning light will be displayed. This will be a different message depending on make and model, and a warning light or message may be displayed on the driver instrument cluster.
To effectively troubleshoot the non-functioning cruise control in your 1998 BMW 740i, start by connecting a code reader to the vehicle. This will allow you to check the functionality of the on-off switch and the set/resume switch, which are critical components of the cruise control system. Next, verify the operation of the brake and clutch switches, as these can interrupt the cruise control when engaged. It's also important to check for any diagnostic trouble codes, particularly code 82, which indicates a problem with the cruise control cancel circuit. Additionally, ensure that the speed sensors are functioning correctly and that there are no warning lights related to the ABS or speed sensors, as these can affect cruise control performance. Inspect the cruise control buttons on the steering wheel to confirm they are sending the correct signals, and finally, check if the Cruise Enabled/Engaged lamp illuminates in the speedometer, indicating that the system is active. By following these initial diagnostic steps, you can systematically identify and address the issues affecting your cruise control system. If these steps do not resolve the problem, further investigation may be required.
When diagnosing cruise control issues in a 1998 BMW 740i, it's essential to consider several common problems that could be at play. A malfunctioning steering angle sensor is often a primary suspect, as it plays a crucial role in the system's operation. Additionally, a fault in the control module can disrupt the cruise control functionality, making it imperative to check for any error codes. Low power steering fluid levels can also contribute to the problem, as they may trigger the BMW Active Steering Inactive warning, which directly impacts cruise control performance. Furthermore, a broken speed sensor can render the cruise control unreliable or completely inoperative, so inspecting this component is vital. In high-mileage models, issues with the rear height level sensor or air suspension springs can affect the level control system, potentially leading to cruise control malfunctions. Lastly, if your vehicle is equipped with adaptive cruise control, ensure that the settings are correctly configured, as disabling them through diagnostic tools may restore normal functionality. By systematically addressing these potential issues, DIY enthusiasts can effectively troubleshoot and resolve cruise control problems in their BMW 740i.
Addressing the non-functioning cruise control in a 1998 BMW 740i is not just a matter of convenience; it is a critical safety concern that should be prioritized. When cruise control fails, it can lead to erratic vehicle behavior, such as unexpected surging or speed fluctuations, which can significantly increase the risk of accidents. Moreover, the malfunctioning cruise control may interfere with other essential systems, such as the electronic logging device (ELD), which is vital for compliance in commercial driving scenarios. Ignoring these symptoms can result in more severe issues down the line, potentially leading to costly repairs or even compromising the vehicle's overall functionality. Therefore, it is crucial to troubleshoot and resolve cruise control problems promptly to ensure a safe and comfortable driving experience, especially during long journeys where this feature is most beneficial. Taking action now can prevent further complications and enhance the reliability of your BMW 740i on the road.
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