good morning

The following is a solved fault on a Ford Focus year 2009 with error U1900 bus communication in the instrument cluster memory .

Problem

With the vehicle in gear, a message appears in the central panel display with the words ENGINE FAULT and the car slows down almost to a standstill. The engine remains at idle and does not pick up the throttle, i.e. when accelerating it does not pick up the revs. In some cases, it also happens that the engine shuts off when approaching a junction. The fault occurs both when the engine is hot and cold. Switching off the engine and restarting it causes the fault to disappear.

Solution:

You have to disassemble the panel and then access the internal circuit board. Repair and/or re-solder the instrument panel circuit board.

The cause of the problem is related to the specific mode of the CAN line in this car . In the Focus series, the relevant information passes through the instrument panel. When this does not function, the car may not respond to the accelerator or the engine may not start and/or switch off while driving.

This instrument panel uses two different CAN buses: one with a speed of 125 kbps (medium speed) and the second with a speed of 500 kbps (high speed).

Specifically, the resistance signal from the electronic accelerator pedal is sent to and received by an independent pin in the 32-pin connector (located behind the ignition) and then converted into a CAN message, allowing the signal to become useful for the engine management ecu, i.e. the Powertrain Control Module (PCM).

Therefore, the PCM is completely dependent on the instrument panel: when it fails, no signal is emitted from the accelerator pedal. In the event of a fault, the accelerator pedal does not act and the engine does not accelerate.

Good reading

Kind regards Antonio