A “Starting System Fault” message accompanied by the P161a diagnostic trouble code (DTC) can be a frustrating experience. This code indicates a communication issue between the Body Control Module (BCM) and the Powertrain Control Module (PCM). The PCM isn’t recognizing the BCM’s ID, preventing the engine from starting. This article will explain the P161A code, its potential causes, and solutions.
Understanding the P161A Trouble Code
The P161A code signifies an “Incorrect Response From Immobilizer Control Module.” Essentially, the BCM, responsible for various body functions including security, sends an identification signal to the PCM, which manages the engine and transmission. When the PCM receives an ID that doesn’t match its stored memory, it triggers the P161A code and prevents the engine from starting as an anti-theft measure. This is a crucial component of the Passive Anti-Theft System (PATS).
Causes of the P161A Code
One potential cause of the P161A code, particularly in vehicles with aftermarket modifications, is a conflict with performance tunes. Modifications to the vehicle’s software can sometimes disrupt communication between the BCM and PCM. Other potential causes, though less common, include a faulty BCM or PCM, wiring issues within the communication network, or a low battery voltage disrupting the system’s operation.
Solutions for the P161A Code
Uninstalling any aftermarket tunes is the first recommended step if you encounter this code. This often resolves the conflict and restores normal communication. Other solutions include resetting the vehicle’s parameters, resetting the ECU (Engine Control Unit), or performing a KAM (Keep Alive Memory) reset. Disconnecting the battery for a period can also sometimes resolve temporary glitches. If these simpler solutions fail, a trip to a qualified technician for diagnosis and repair might be necessary to address potential hardware or wiring problems. The Ford service manual recommends a “Passive Anti-Theft System (PATS) Parameter Reset” as a potential fix, detailed in section 419-01C.
Resolving the Starting System Fault
Addressing the P161A code often involves resolving the underlying communication issue between the BCM and PCM. While uninstalling aftermarket tunes proved effective in one instance, other solutions like resetting various vehicle systems or addressing potential hardware problems may be necessary. Consulting a professional technician is recommended if the problem persists.
