BMW Intermittent Warning Lights and Fail Safe Mode

A BMW may show warning lights on the instrument cluster when warmed up and could even go in fail-safe mode. The warning lights may come up intermittently. The vehicle returns to regular operation after the car is restarted or cooled down. 

In this guide, you will learn about common issues that can cause intermittent BMW problems.

Symptoms

• Intermittent loss of power
• ABS / Brake / Traction Control light on
• Transmission won't change gears.
• Stuck in fail-safe / limp mode
• Random warning lights on the dash
• Intermittent warning lights

Typically allowing the car to cool down, restarting it, or clearing the codes, will enable the vehicle to run normally. 

A BMW can get stuck in gear intermittently when the transmission fluid is low or the on-board voltage drops while the engine is running. If you have a BMW that loses power, gets stuck in gear (fail-safe mode), the first thing you need to do is to check the transmsion fluid level and ensure you have a good battery that holds a reasonable charge.  

 If the transmission fluid level is correct, the next troubleshooting step is to read the fault codes from all modules. 

Possible Causes

• Gear selector 
• Transmission control module (EGS)
• Engine control module (DME / DDE ) 
• Weak battery 
• Requires DME / EGS software update
• Faulty temperature sensor
• Low transmission fluid level
• Engine temperature sensor
• ABS faults

Any of these modules could have an internal fault. A defective connector or damaged wire harness can also be the problem.

The problem can be due to a fault in the CAN-BUS network issue. The typical modules that run on the CAN-BUS II are the gear selector, engine control unit, and transmission control module. 

The next step is to read the codes from all the modules listed above. 

How to diagnose BMW intermittent problems

The next step in diagnosing BMW intermittent issues is to read the fault codes from all the modules and determine the next steps. To read fault codes from all the modules, you will need a specifically designed scanner for BMW. 

1. Locate the diagnostic port under the dashboard. 
2. Plugin in your scanner. 
3. Turn on the ignition and your BMW scanner. 
4. Select your BMW model. 
5. Select to run a full system scan. Depending on the scanner, it will show as Health Report, Full Scan, or Quick scan. 
6. Analyze all the fault codes that show as current or intermittent. 

After reading the code, you should have a better idea of what to focus on next. 

Intermittent Codes

A BMW with the following fault codes may have a bad engine control unit, shifter module, or transmission control module. The most likely cause is a faulty transmission control module, which in most BMWs is installed inside the transmission on the valve body. 

DME / DDE Engine  Codes

• CD950F - No message request torque crankshaft transmission 2 0xA0, receiver DME/DDE, tranmitter EGS
• CD94ED - No message data display transmission, 0x3FD, reveiver DME / DDE, transmitter EGS
• CD94DC -- Electronic transmission control EGS, PT CAN, PT-CAN2, Communication Fault
• CD94C3 - No message diagnostic OBD transmission, 0x396, receiver DME / DDE transmitter EGS
• CD94BA - No message, display, engine speed, dynamization, receiver DME / DDE/ EGS transmitter
• CD9487 - No message request torque crankshaft, transmission, receiver DME / DDE, transmitter EGS
• CD946B - No message status transmission control unit, receiver DME / DDE, transmitter EGS. 
• CD9469 Message, status transmission control unit, signal invalid. 

EGS Transmission Codes 

• 4209A4 - Temperature sensor, Hotmode 3 excess temperature with possible damage to transmission coolant line detected. 
• CF047F - EGS, PT-CAN2 Communication Fault
• CD1701 - Signal gear selector switch status, total communication failure, invalid transmitter GWS. 
• CF17A1 - No message status, gear selector switch, receive EGS, transmitter GWs. 
• CF17B1 - No message status, gear selector switch, receiver EGS, transmitter GWS

It is important to note that BMW's irregular fault codes can be very challenging to diagnose. We do not recommend replacing any of the parts or components listed here without first performing a diagnostic.