what would be the cause of the check engine light on a 93 400E? I dont know where to start looking. Any help would be greatly appreciated, thanks in advance.

 

02 sensor to start...after that about 30 other things... mine still coems on...it's been checked the car runs fine everything is in order and the 02 sensor has been replaced. we currently think its the air flow sensor whcih is throwing a code...

 

Gotta start with the code. I wouldnt just throw parts at it until the light went off. Take it to the shop. And theres no such thing as "the light just comes on at certain milleage" It's wired to a ton of electrical sensors, leaving you with 30-130 possibilities.

 

Don't the 93 models come with a built-in code reader? Mine is under the hood near the battery. It has a cover on it.

 

Yes, it has a built in code reader, I count 19 flashes. It says something that the emissions are at its limit. I have already changed the o2 sensor and the light went away and then came back on. I know when I took it in for a smog the hydrocarbons were very high. This problem is not fun to hunt down. Thanks for the suggestions everyone, please keep them coming. Hopefully one of the fixes will work.

 

Did you check if there is more than one code? You have to repeat the code reading process until the codes repeat.

It sometimes helps to read the Pin 8 and Pin 14 codes for more detail on the problem.

Here's a link to build the code reader. Use an empty film can to mount all the components.

Code reader

The middle banana plug goes into either Pin 8 or Pin 14 to read the ECU and CC/ETA codes. Here's a list of the codes:

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

I keep both the code reader and the code list in my car, in case I'm on the road and the check engine light comes on.

If you get to the bottom of your problem, please post the fix. My car just started throwing a Code 19 and I plan on changing the O2 sensor, hoping this'll fix the problem. My Pin 8 shows Codes 13 and 20.

 

Ok I know it has been quite sometime. I tried to do the code reader thing but when I went to look at the correct pin numberes there were no contacts so I decided not to build the code reader. The car was put on the diagnostic test and it determined something about the oil pressure sensor in the engine. He says that the computer is detecting something with the oil pressure when the engine is not warmed up. Some of the symptoms are detected when the engine is cold are the noisy cam lifters ticking, other high pitched whizzing such noise. When the engine warms up the noises stop. The mechanic/service advisor at the independent shop said that the car would need a entire engine. He says when it come time for the somg test and the check engine light can not be corrected it will fail the emissions visual check. He says that this is a very expensive repair.
The shop said that there are no other codes dealing with the emissions system so it should pass if only the check engine light is off.
Thanks for all the suggestions everyone.

 

Where in Ca are you located?

 

Im currently in Fresno area, The car went to LA area for some repairs.

 

ok this is the code that keeps coming up.

19 Injectors circuit open or circuit short emission control module adaptation in engine control module at limit.

any help with understanding what is actually means will be greatly appreciated.

 

My car still shows a code also, even though I replaced the O2 sensor. This time only get:
Code 4 (Air injection system faulty hot film mass air flow sensor with hot wire), and
Pin 8, Code 13 (O2S [Lambda] control system operating at rich or lean limit).

After talking with a knowledgeable person, I strongly suspect I have a bad Air Mass Meter (more commonly known as the air flow sensor). This may be your problem as well. They cost $300 each. I understand you should stay away from the $160 units sold on eBay and buy only Bosch-manufactured units.

 

I know last time when the car was running really bad, the MAS was bad. The car would not idle at that time. I had to have the car towed to the shop.
Have you ever tried any of the chemicals to clean the MAS? I picked up a can but was kind of afraid to spray it in without taking off the sensor.

On the Pin 8 I dont have any metal contacts in the connector so i cant check that. I just see straight thru the connector.

 

why would you need a whole engine for a faulty oil pressure sensor?

Sound fishy to me.

May want to drive down to my mechanic in the los angeles area. he wont tell you your car needs something it doesn't.

I have to get my car smogged and the CE light is on, but I know the problem is the air pump. I plan on just resetting the light right before I go do the smog test and it shouldn;t come back on for several days anyway.

 

Ya, I know those mechanics didnt even give me a print out of the diagnostics. I was like what are these guys smoking. I was able to get the light to reset for about a week and now its back on. The last time I took the car In for a smog it didnt pass. At 15 mph its HC max is 81 it measured at 275, NO max is 685 it measured at 883. CO max is .47 it measured .48. I recently changed the O2 sensor I might have to replace it along with a new cat. Any ideas?

 

I would take it to a mechanic who you trust who can adjust the car properly.

Also make sure you drive the car for a while before taking it in for the smog and don't let it sit before the test. You need everything nice and hot.

You could also try some of the pass smog in a bottle stuff. it is supposed to get the cat nice and hot which is supposed to help witht he emissions.

 

My 1994 E420 is reading this code. Any resolution? I know this is 10 years later. Lol