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E39 1999 - 523i Transmission Failsafe on Warm start

4K views 5 replies 1 participant last post by  arh 
#1 ·
I have a strange problem with my car. I previously had warm start issues that were solved by replacing the crankshaft sensor. Everything has been fine for a few months.

I then had warm start issues again and my garage diagnosed the issues as a stuck throttle (error codes were showing this). I got this replaced with a used unit and the car drives much better and throttle response is very good. Unfortunately this has not solved the warm start issue as the error codes have now changed. If I start the engine when cold I have no issues. If I drive around and let the engine warm up then it will not start and even before I crank the engine the Transmission Failsafe Failure message comes up.

The errors from diagnostics are below:

110 - signal pedal travel sensor
112 - signal throttle sensor potentiometer
169 - Engine throttle output stage shutoff diag
171 - Plausibiilty system engine throttle
115 - Reference voltage 1 pedal travel
021 - Activation VANOS solenoid valve inlet
019 - Activation VANOS solenoid valve exhaust
053 - Activation idle speed control valve opening
027 - Activation idle speed control valve closing
217 - Signal CAN EGS
130 - Signal CAN ACS
068 - Activation solenoid valve

These errors automatically clear themselves after 5-10 minutes and the car will start again with no issues.
The car always starts fine straight away but if I wait for 30 seconds it fails every time. I then need to wait for 5-10 minutes and then the car will start again with no issues. I have no problems with idle or throttle response.
The DME adaptations have been cleared in the throttle.

Does anyone have any ideas on what could be wrong? This is a real pain as I get stranded when getting petrol. My garage thinks it may be the fuel pump?

Thanks.
 
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#5 ·
From another forum I have found the info below. Seems to match?

The DME Relay is the blue one in the ECU compartment (passenger side, behind the strut). This relay is turned on by the main DME ECU. The ECU has several power suplies to make sure it's always watching but the DME relay is the power switch for all the sensors in/on the engine (well most anyway), on failure it will stop your engine.

The DME relay is turned on by the ECU by internally switching it to ground, it has a constant live feed from the junction box. The junction is about the size of a pound coin and has red cables going to it. Both cables are quite large. The junction box has normally two to three pins on it and is located in the same ecu compartment near the relays.

Also inside the ecu box you'll see a small collection of fuses, the fuse we are interested in is fuse 3. Find a good place to test with your multimetre. Next turn on the ignition and test both sides of the fuse (to ground) while everything is fitted. You should get 12v on both occasions, if you dont and get it only one side - change the 20A fuse. If you get nothing close to 12v then change the relay, but let me know first and i'll show you where to test for wiring faults.

Using scan gear:

These faults will indicate a failing DME Relay:

(019) 13 - Activation, VANOS solenoid valve, outlet
(021) 15 - Activation, VANOS solenoid valve, inlet
(027) 1B - Activation, idle actuator/closing coil
(053) 35 - Activation, idle actuator/opening coil
(068) 44 - Activation, solenoid valve, fuel tank ventilation
(110) 6E - Signal, driver's request sensor, potentiometer1
(112) 70 - Signal, throttle position sensor, potentiometer1
115) 73 - Reference voltage, voltage regulator 1
(170) AA - Control unit self-test, motor-driven throttle valve or internal fault
(171) AB - System plausibility, motor-driven throttle valve


These fault codes are entered in the above list if the system voltage was too low due to battery discharge or due to failure or contact fault of the DME main relay.
 
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