BMW Glow Plug Learning
Supported coding features by BimCOM diagnostic tool https://www.obdtester.com/bimcom
1. Glow plug set save mode (before replacing) - make this coding before replacing
2. Glow plug reset (after replacing) - make this coding after replacing
1) Glow Plug Set Save Mode (Before Replacing)
What it does
- Saves the current glow plug calibration values in the ECU
- Stores:
- Aging characteristics
- Resistance trends
- Activation times
- Temperature response profile
- Ensures correct comparison after replacement
Why it is required
- Glow plugs degrade over time:
- Higher resistance
- Slower heating
- Inconsistent pre-glow and post-glow behavior
- ECU must know the old values to correctly adapt new ones later
Conditions that must be met
- All glow plugs still installed
- Engine cold or at moderate temperature
- No active glow plug circuit faults
- Battery charger connected for stable voltage
- Glow control module functioning correctly
When the procedure should be performed
- Before removing or replacing glow plugs
- Before replacing the glow plug controller (GSR module)
- Before diagnosing hard starting related to the glow system
What happens during the procedure
- ECU reads and stores individual glow plug behavior
- Measures:
- Electrical resistance
- Heating curve
- Required activation duration
- Data is saved for later adaptation reset
If the procedure is skipped
- ECU may miscalculate new glow plug values
- Hard starting may persist
- Possible glow system faults even after new plugs are installed
- Incorrect post-glow timing
2) Glow Plug Reset (After Replacing)
What it does
- Clears old glow plug adaptation values
- Tells the ECU that:
- New glow plugs are installed
- New heating characteristics must be learned
- Resets:
- Activation duration maps
- Temperature-based correction factors
- Resistance learning data
Why it is required
- New glow plugs have:
- Lower resistance
- Faster heating
- Different energy requirements
- Old learned data causes:
- Overheating
- Underheating
- Incorrect pre-glow time
Conditions that must be met
- New glow plugs installed and properly torqued
- Glow plug controller connected and functional
- No wiring damage to the glow circuit
- Battery stable (charger recommended)
- No active glow plug or control module fault codes
When the reset should be performed
- After installing:
- New glow plugs
- New glow plug control module
- After fixing wiring or connector issues related to glow plugs
- After resolving glow plug circuit faults
What happens during the procedure
- ECU clears previous adaptation data
- Starts a new learning cycle
- Monitors:
- Resistance of each glow plug
- Heating speed
- Current draw stability
- Updates internal glow system maps
If the reset is not performed
- Hard starting, especially in cold weather
- Increased emissions during cold start
- Glow plug warning light may remain active
- Risk of premature glow plug wear
- Rough idle for first few seconds after startup
After the reset
- Start the engine and allow it to idle
- Monitor glow plug activation values in live data
- Ensure no glow system faults return
- Confirm smooth cold starts on next morning