What does it mean?
When I have diagnosed a stored code B1208, it has always meant that either the instrument panel controller (IPC), body control module (BCM), or the powertrain control module (PCM) has detected a problem with a particular electronic instrument cluster (EIC) switch assembly. This particular code indicates that a circuit within the switch assembly has shorted to ground. In automotive related electronic instrument clusters, there are typically two (manually operated) switches integrated.
The first of these switches is used to reset the odometer trip counter and the second is used to convert the display from standard to metric units of measure. Switch-1 denotes one of these switches but is not uniform across all makes and models. What is referred to as Switch-1 in one particular vehicle may be referred to as Switch-2 in another, of a different make (and vice-versa).
Consult a reliable vehicle information source, such as a professional technical data service for specifics as they pertain to the vehicle in question. The switch which controls the level of instrument panel illumination (when the headlamps are on) is typically integrated into the headlamp switch. If a shorted circuit in the designated EIC switch is detected by the BCM, or one of the other controllers, a code B1208 will be stored and a service engine soon lamp may be illuminated.
In some models, instrument panel data illumination may be dimmed in order to make the driver aware that a malfunction has been detected and a code has been stored in the BCM.
Symptoms
- Trip odometer resets by itself, or cannot be reset at all
- Display unit of measure changes on its own, or the change cannot be made
- On some vehicles the instrument panel data illumination is dimmed on purpose to alert the driver
- Warning lamp illuminated with the code stored
- Cluster display frozen or cycling through screens without any button press
- The fault appears the moment the switch is pressed
Likely causes
- Switch mechanically stuck in the pressed position, or its contacts welded/shorted internally
- Signal wire chafed against the cluster housing, a dash brace or a mounting bracket
- Moisture or a spilled drink inside the cluster or the switch assembly
- Harness pinched behind the dashboard after cluster, audio or heater work
- Terminal pushed out of the connector and touching the metal dash support
- Poor repair splice or an aftermarket accessory tapped into the switch circuit
- Failed input circuit in the module that monitors the switch (IPC, BCM or PCM depending on the vehicle)
How to fix it
- Press and release the switch while watching its reported state in live data to confirm the circuit is stuck low
- Remove the cluster or switch assembly and check whether the button is mechanically jammed or contaminated
- Unplug the switch and measure the signal circuit to ground; if it is still shorted, the fault is in the harness
- Inspect the harness behind the cluster for chafe, pinch points and pushed-out terminals
- Check for water ingress from the windscreen seal or the heater box in that area
- Repair the harness fault, or replace the switch/cluster assembly if the short is internal
- Replace and configure the monitoring module only after the circuit is proven good, then clear the code and confirm the trip and unit functions work