The P1542 code is a common issue for BMW owners with the M52TU engine. This article discusses troubleshooting this code using an Autozone scan tool, focusing on a 1999-2000 BMW with the 2.8L M52TU engine and Siemens MS 42.0 engine management system. This system utilizes a cable-driven throttle connected to a servo motor on the throttle body.
The P1542 code often manifests as a rough running engine, limited to approximately 1200 RPM. While the engine idles smoothly, thanks to the Idle Control Valve (ICV), attempting to accelerate beyond 1200 RPM results in a loss of power. The ICV allows for brief revving to 3000 RPM, but sustained acceleration is impossible. Restarting the engine often temporarily resolves the issue.
One possible cause is a failing throttle body servo motor. The servo may not be receiving the correct signal from the throttle cable, or internal wear within the servo could prevent proper throttle plate movement.
Before replacing the throttle body, checking the throttle cable play is crucial. The Bentley manual specifies a maximum play of 1.5mm at the throttle body end. A captive adjustable plastic collar nut on the cable allows for adjustment. Incorrect cable adjustment can disrupt the signal to the servo, triggering the P1542 code.
An Autozone scan tool can be invaluable in diagnosing this issue. While the initial symptoms might not immediately trigger a code, eventually the Check Engine Light (CEL) and the EML light will illuminate. The Autozone scan tool can then be used to read the specific code, confirming the P1542 diagnosis. Clearing the code with the scan tool allows for continued driving but doesn’t address the underlying problem.
In this specific case, after clearing the P1542 code with an Actron scanner, the car functioned normally for a time. However, the recurring nature of the problem suggests a more permanent solution is needed.
Further diagnostics may involve inspecting the throttle body for obstructions or damage. If the throttle cable adjustment and visual inspection don’t resolve the issue, replacing the throttle body and reprogramming the adaptive values with a BMW GT1 dealer computer might be necessary. Using an Autozone scan tool to regularly monitor for recurring codes is recommended. This allows for early detection and potentially prevents further damage. Addressing the underlying issue promptly will ensure optimal engine performance and prevent potential breakdowns.
