stalling

I have replaced in tank fuel pump and cam driven pump but when outside temps are high vehicle engine will stall when coming to a stop. Will restart after sitting a short while. Is there a relay or something else that may be failing causing this condition only on hot days?

5 speed or Auto


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test your 109 relay

automatic - what is relay 109 and location? car is a 2004 Jetta TDI automatic

Over your feet as you’re sitting in the drivers seat, under the dash. There is a relay panel, the
109 sits right on top of the 377 (wiper) relay. Remove that to have better access to the 109.
If your 109 is black it’s the old style and probably bad. At less the $20 I’d just replace it. Many of us keep a spare anyway.


The 109 powers the ecu. No electric to the ecu and the car won’t start or shuts off while driving. Usually they fail intermittently and then altogether. A sure sign of a bad 109 is the glow plug light does not come on when you first turn the car on to glow it.

I will definitely replace this relay. A point of interest I noticed that the glow plug light flashes on and off when you try to start after car stalls. When car cools down light is normal and motor starts.

Check to see if you have any fault codes. Flashing glow plug light means there's a code set, but there's a whole list of codes that could be set.

still stalling

I replaced 109 relay and put about 150 miles on vehicle then it stalled again on a warm day. Restarted and ran fine after sitting a couple of minutes. I checked fuel filter and no indication of problem. The check engine light did come on after vehicle stalled. Trouble codes read were PO725 and P2637. Codes were erased and have not reoccurred. This problem only occurs when outside temperatures are relatively high. Is there another electrical relay that may be failing when temperatures are high? How about ignition switch? Any suggestions for troubleshooting would be appreciated.

Is it a PD or a VE engine? You might check the various temperature settings with VCDS (or equal). Check each cold (ambient) and hot (operating temp). Couldn't find either of those codes in the Ross Tech wiki.

crank position sensor - I'd bet on it... Mine did that for ages at idle, but never caused a check engine light. I've seen that people have had luck testing by wiggling the sensor wires at idle - if it stalls it's a sure sign the sensor is bad.

2004 Jetta BEW I will look into Crank Position Sensor

Best guess yet. Do check the wires first, they do sometimes get damaged.

gforce1108 said:

crank position sensor - I'd bet on it... Mine did that for ages at idle, but never caused a check engine light. I've seen that people have had luck testing by wiggling the sensor wires at idle - if it stalls it's a sure sign the sensor is bad.

Click to expand...

I can relate. No DTC's either. A new crank sensor fixed the stalling.

From Rosstech:
"I get the following codes: P0725/P1780/P1850 also have no power to fuses numbered 32,34 and 43"

Check fuse 176 (110A) over the battery.
Dirty or bad connection.
It feeds the 3 fuses above.

I replaced crank position sensor and have driven 300 miles with no stalling. That appears to be the problem. Thanks for all your help!