BMW DTC P177B – TCM Internal Correlation Error Displayed / Real Transmission Position
DTC P177B meaning on BMW
DTC P177B on a BMW indicates a Transmission Control Module (TCM) Internal Correlation Error. This error occurs when the TCM detects a discrepancy between the expected transmission position and the actual transmission position.
BMW DTC P177B symptoms
Symptoms of DTC P177B on a BMW may include erratic shifting behavior, transmission slipping, harsh shifting, or the transmission not engaging properly. The vehicle may also go into limp mode to prevent further damage.
BMW DTC P177B causes
The most common causes of DTC P177B on a BMW include a faulty transmission range sensor, a malfunctioning TCM, wiring issues, or a mechanical problem within the transmission itself.
BMW DTC P177B seriousness
DTC P177B on a BMW should be taken seriously as it can lead to further transmission damage if not addressed promptly. Driving with this error present can cause additional stress on the transmission components and may result in costly repairs.
How to diagnose DTC P177B on BMW
To diagnose DTC P177B on a BMW, a diagnostic scan tool capable of reading transmission fault codes is needed. The technician will need to inspect the transmission range sensor, check for any wiring issues, and perform a thorough inspection of the TCM and transmission components.
How to fix DTC P177B on BMW
Fixing DTC P177B on a BMW may involve replacing the transmission range sensor, repairing any damaged wiring, or reprogramming the TCM. In some cases, a transmission fluid flush and filter replacement may also be necessary to ensure proper transmission operation.
How to erase DTC P177B on BMW
To erase DTC P177B on a BMW, a diagnostic scan tool capable of clearing fault codes is required. Once the underlying issue has been addressed and fixed, the technician can use the scan tool to clear the code and reset the TCM. It is important to verify that the error does not return after clearing it.
Recommended tools & DTC Scanners for BMW
Best Diagnostic App for modern BMWs: BimmerLink
Recommended Bluetooth adapter for Bimmerlink: OBDLink CX
Cable adapter for Bimmerlink: Enet Cable USB Type C
For older BMWs we recommend: Autel AutoLink AL319 (2024 version)
Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter
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