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Old 08-07-2019, 01:49 PM
chazola's Avatar
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Join Date: Nov 2003
Location: London, United Kingdom
Posts: 1,241
W124 M104 DTC Help please

Hello, my '93 320TE (M104.992) has thrown code number 49 on pin 8 (HFM)- which according to the code list is 'Voltage supply circuit 87 U at engine control module (N3/4) implausible/low voltage' linked to ground W10/1- I can't seem to find out anything more searching online about the cause of this fault- symptoms are rich running (can smell excess fuel at cold start), poor economy and hesitation/ lack of throttle response.

1993 320TE M104

1983 230E W123 M102
1994 E300D S124 OM606 (x2)
1967 250SE W108 M129
1972 280se 3.5 W108 M116
1980 280SE W116 M110
1980 350SE W116 M116
1992 300E W124 M103
1994 E280 W124 M104
"music and women I cannot but give way to, whatever my business" -Pepys

Last edited by chazola; 08-07-2019 at 02:02 PM.
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Old 04-07-2021, 12:36 PM
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Join Date: Mar 2021
Location: Poconos, PA
Posts: 1
I hate to bump such an old thread, but a lot of the threads across differing forums end up without anything conclusive.

I too have this code and similar symptoms. I've currently got an OVP sensor en route from a friend to test with, and understand the wiring harness can be shoddy/failed...but I'm avoiding paying for one before going much further.

Car runs fine when cold/start up, but does have excess fuel smell. As soon as it comes into operating temp it runs mostly fine at speed, but low speed hesitation and wonky idle when coming to stop lights. Yes I can drive around it, but don't want to find myself stranded either.

Pin 8 Faults 42 and 49
Pin 3 Fault 17
Pin 14 Faults 3 5 and 6
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Old 04-08-2021, 03:05 PM
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Join Date: Aug 2002
Location: Southeastern PA
Posts: 3,077
As for the fuel smell, you might want to remove the air cleaner and inspect the EHA valve for leaks when you start the engine. If the EHA valve body is wet, the EHA valve body likely has a hairline crack in it and needs to be replaced. The hesitation issue may be related to a faulty Oxygen sensor. When was it replaced last? As far as I know they should be replaced every 60,000 miles on that vintage vehicle.
Fred Hoelzle
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Old 04-08-2021, 05:28 PM
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Join Date: Feb 2007
Location: los angeles
Posts: 796
load test your battery, make sure its good

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