'94 E320 cabrio m104. Has built in LED code reader. Pressed the button and it then flashed 4 times. I do not have the homebrew code reader to check the other modules but I got the 4.

which means?

Code #4 from the diagnostic module suggests a problem with the air mass sensor.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

oh wonderful

Well it was not illuminated today. I suppose I should start checking the wires

I just built a reader, since plugs and switches came in pairs I bought enough parts to make 2. It should cost you less than $10 at Radio Shack.

__________________
'88 300TE, 175k, black RENNTech 3.6L Recaro C's AMG 1 SOLD
'92 500E, 110k, Spruce green, stock SOLD
'94 E320 Cabriolet, 130k, E500 wheels, Emerald green SOLD
'94 E320 Cabriolet, 110k, black, stock, SOLD
'88 300TE, 229k, dark grey, SOLD
'90 300CE, 212k, white, new paint, SOLD
'91 300E, 209k, white, rebuilt head SOLD
'74 914-6, grey, 2.7L 325hp twin turbo Audi conversion

Well the light came back on and has been on for two days now and its code #4

I have the stuff to build the home brew reader but is that even necessary now?

Can I just clean the MAF?

I'm about to drop $250 on the air mass sensor.. I want to verify that code 4 from the CEL module is the air mass sensor.

note I do not have the diy code reader. I just pressed the button on the module and it flashed 4 times.

I cleaned the maf today and tried to reset the code yet when I hold the button down for 4 seconds and wait I get no blinks and the CEL is still on.

wtf?

Code 4 is air injection inoperative. The next step is to read the codes on the HFM which is pin 8. You need to build the code reader.

somewhere in these forums, a very clever MB mechanic explains the BITE diagnostic system, the steps to find the "true" code. the blinks from the built in button only lead to another set of pins which blink with reader but that also is only a general area of fault but closer to true fault and fix. Keep searching the forums and build the code reader, I did and it works great. Good luck, FYI if car runs fine some people disconnect the CEL.

I've got mostly everything to build the code reader just need to get some wire.

The light went out finally after I reset the codes. But my fuel economy just seriously tanked.

example, with my normal driving and occasional AC use the first bit of the fuel guage from full to the next hash mark is around 90 miles.. then to half a tank the total is around 180-185 miles. Today... 117 miles. I'm waiting to see how the full tank goes. I'm going to double check tire pressure tomorrow

I think you're wrong. According to this thread (E320 16 PIN DTC Charts inc. pin 8, pin 14) "4 Air injection system faulty hot film mass air flow sensor with hot wire from the" diagnostic module(led button deal). But I do need to build the code reader to check pin 8

I know the air pump works because it turns on when it should

I miss owning a diesel.. none of this electronic crap

The factory shows it as just "air injection inoperative" - which doesn't necessary mean the air pump is bad. Typically the DM only scratches the surface - again you need to read the other codes as the factory suggests. The Baum book is great but it has quite a few mistakes - for example "hot film mass air flow sensor with hot wire" is complete gibberish. Hot film sensors don't have a hot wire.

http://www.startekinfo.com/manual/volumes/e3/8_4/m11.jsp

well then. Code reader I will build.

What guage wire do you suggest. I need to pick some up.

Any gauge is fine, doesn't need to be big, maybe 18 or 20, hardware store should sell by the foot.

Emissions - Using Built-in Diagnostic Module
1 No Fault Found
2 Heated oxygen sensor faulty
3 Lambda control faulty
4 Air injection system faulty hot film mass air flow sensor with hot wire
5 Exhaust gas recirculation faulty
6 Idle speed control faulty
7 Ignition system faulty
8 Engine coolant temperature sensor open circuit
9 Intake air temperature sensor, open circuit
10 Voltage at mass air sensor too high/low
11 Tn-signal (rpm signal ) at engine control module faulty
12 Heated oxygen sensor heater circuit open or circuit short
15 Injector, cylinder 2
16 Closed throttle position information faulty
17 Data exchange malfunction between individual control module
18 Adjustable camshaft timing solenoid circuit open or circuit short
19 Injectors circuit open or circuit short emission control module adaptation in engine
control module at limit
20 Vehicle speed signal not present
21 Purge switchover valve circuit open or circuit short
22 Crankshaft position sensor signal faulty
23 Intake manifold pressure (in base module pressure sensor-) with engine running too
high/low.
24 Starter ring gear segments and /or crankshaft position sensor faulty
25 Knock sensors or engine control module faulty
26 Upshift delay faulty
27 Not used
28 Engine coolant temperature sensor (engine coolant temperature change monitor )
44 Not used
45 Fuel safety shut-off electronic accelerator or cruise control active
46 Resonance intake manifold switchover valve
47 Not used
48 Not used
49 Voltage supply at engine control module 8v
50 Engine control module
_________

PIN 8 ECU
1 No fault found
2 Engine Coolant temperature sensor
3 Intake air temperature sensor
4 Hot film mass air flow sensor
5 CTP switch
6 Not used
7 Not used
8 Idle speed control (ISC) system at upper or lower control stop or CC or EA indicates "limp
home" mode.
9 O2S 1 (before TWC) - voltage too high, circuit open or voltage implausible
10 O2S 2 (after TWC)voltage too high, circuit open or voltage implausible
11 O2S 1 heater (before TWC) - Current too high/low or short circuit.
12 O2S 2 heater (after TWC) - Current too high/low or short circuit.
13 O2S (Lambda) control system operating at rich or lean limit
14 Injector, cylinder 1
15 Injector, cylinder 2
16 Injector, cylinder 3
17 Injector, cylinder 4
18 Injector, cylinder 5
19 Injector, cylinder 6
20 Self-adaptation at idle speed or upper/lower partial load at rich or lean limit
21 Ignition output 3 or ignition coil for cylinder 1 and 6
22 Ignition output 1 or ignition coil for cylinder 2 and 5 (Engine 111, cylinder 1 and 4)
23 Ignition output 2 or ignition coil for cylinder 3 and 4 (Engine 111, cylinder 2 and 3)
24 CKP sensor or magnet for position sensor not recognized
25 CMP sensor not recognized or implausible
26 Not used
27 TN-signal (rpm signal ) - open or short to ground
28 VSS - open circuit
29 Not used
30 Fuel pump relay module - open or short circuit
31 Not used
32 Knock sensors 1 and /or 2
33 Maximum retard setting on at least one cylinder has been reached or the ignition angle
deviation between the individual cylinders is greater than 6 degrees crankshaft angle
34 Knock control-output switch in engine control module faulty Momentary fault in
self-adaptation closed throttle speed/partial load
35 Model 124,129 and 140 AIR pump switchover valve and/or electromagnetic AIR pump
clutch. Model 202 AIR pump switchover valve and/or AIR relay module
36 Purge control valve - open/short to ground or B+
37 Upshift delay switchover valve
38 Adjustable camshaft timing solenoid - open/short to ground or B+
39 Exhaust gas recirculation switchover valve - open/short to ground or B+
40 Transmission overload protection switch - open/short to ground or B+ or open or closed or
implausible
41 CAN communication from engine control module faulty
42 CAN communication from ASR, EA/CC/ISC module or diagnostic module (OBD II) faulty
43 Starter signal (circuit 50) not present
44 Not used
45 Fuel safety shut-off of electronic accelerator or cruise control active
46 Resonance intake manifold switchover valve - open/short to ground or B+
48 O2S 2 (after TWC) heating circuit relay module - open/short to ground or B+
49 Voltage supply at engine control module implausible/low volts
50 Engine control module faulty or not coded.
____________

PIN 14 CC/ETA
1 No fault found
2 EA/CC/ISC control module (N4/1) or Safety contact switch (M16/1s1) or Stop lamp
switch or Cruise control switch or Actual value potentiometer or Starter lock-out/back-up
lamp switch or engine speed signal or vehicle speed signal or closed throttle position
switch or safety relay in EA/CC/ISC control module
3 Right EA/CC/ISC actuator (left cylinder bank) (M16/1)
4 Cruise control switch (S40)
5 Stop lamp switch (S9/1)
6 Starter lock-out/backup lamp switch
7 CAN data bus signal from EA/CC/ISC, ABS/ASR, HFM-SFI or LH-SFI (right or left)
control module faulty.
8 Left front axle vehicle speed sensor from ABS/ASR control module
9 Left rear axle vehicle speed sensor from ABS/ASR control module or in 124 chassis
Hall-effect speed sensor.
10 Engine speed signal (TN) from base module (LH-SFI) or engine control module (HFMSFI)
11 Closed throttle recognition signal to engine control module (HFM-SFI or Left LH-SFI)
Fuel safety shut-off to engine control module (HFM-SFI or left or right LH-SFI)
12 EA/CC/ISC control module voltage supply
13 Left EA/CC/ISC actuator (right cylinder bank) or actual value potentiometer (M16/4r1 or
M16/4r2) or actuator motor (M16/4m1)or magnetic clutch (M16/4k1).
14 Closed throttle position contact switch
15 CAN data exchange with ABS/ASR control module illogical

__________________

1990 190E 3.0L