c200 1994 is it HMF or PMS
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c200
russel bad news !! suddenly the car stopped i though it was empty fuel !! and now when i check i get no spark on all 4 cylinders !! i checked the coil packs !! tehy are working !! is the OVP relay has to do with ignition ? the OVP pin 31 and 30Z has 624 ohm and the 15u and pin 31 has 1700 ohm !! and it gets hot !! i replaced the ovp a year back !! is my ECU fried ? :O
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From: Cape town
not a merc
Check fuel delivery?
Check for power at terminal block on lf fender (small 7mm nut)
Supplies power to coils and inj.
Ovp supplies power to ecu. Check in wis for all the powers to ecu..
Check at the ecu plug for power.
If All is ok. Also check for inj pulse! Put a long screwdriver or stethoscope onto injector and listen for clicking pulse while cranking. No pulse and no spark..and all powers ok. Look at crank sensor! The last thing we condem is ecu mate. They Do Not just fail!
Check for power at terminal block on lf fender (small 7mm nut)
Supplies power to coils and inj.
Ovp supplies power to ecu. Check in wis for all the powers to ecu..
Check at the ecu plug for power.
If All is ok. Also check for inj pulse! Put a long screwdriver or stethoscope onto injector and listen for clicking pulse while cranking. No pulse and no spark..and all powers ok. Look at crank sensor! The last thing we condem is ecu mate. They Do Not just fail!
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c200
fuel delivery is okay !! i can here the fuel pump working !!
i checked the power to coil packs ! 12 V positive !! injectors positive !!
russel can a bad OVP cause no start in my model !
i checked the ECU connector A for power i get power !!
when cranking the crank sensor generates around 0.2- 3 volts varying !!
i have no other way to determine the state of ECU !!
i checked the power to coil packs ! 12 V positive !! injectors positive !!
russel can a bad OVP cause no start in my model !
i checked the ECU connector A for power i get power !!
when cranking the crank sensor generates around 0.2- 3 volts varying !!
i have no other way to determine the state of ECU !!
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Joined: Jun 2011
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From: Cape town
not a merc
The ovp relay is basically just 3 relays in one housing with an integrated fuse and zener diode. All it does is protect the ecu from over voltage transients of about 22v. Should the voltage across the zener exceed 22v it will start to conduct to ground via the fuse which will in effect cause a short circuit and make the fuse blow. You cannot test the relay using an ohm meter. You need to power it up on the table and test if it has output, but like I said before... just test for power at the ecu first. If power is ok then your ovp relay is Good. If you have a missing power supply then you can check ovp. Don't test with ohm meter. Unplug ecu plug. (Body harness plug) switch ign on. Use a test lamp and check for power on relevant pins.
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Joined: Mar 2008
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mb
Hello,
1. you car have AG4? (your ECU coded for AG4, Japan, KAT [000 019 128])
2. you have wiring diagram for HFM? if not have, download and print scheme 111.960 (it same)
3. you must check idle speed signal (ECU constantly sees (thinks) "idle mode" even when you hit the gas pedal) ).
disconnect "throttle connector", measure the resistance between pin 5 and 6. When the gas pedal is released - 0 ohm or 600 ohm when the gas pedal is depressed - infinite resistance.
If you have such evidence, the more you need to check wiring to ECU (see diagram). Perhaps a short to ground (minus).
ECU sees the 5V signal from the MAF.
you must disconnect the MAF connector and measure the voltage between pin 2-4 and between 2-5.
In both cases should be 11-13V (ignition on).
If you pass this test, I will write how to check the MAF (it will need to connect 2 wires).
As well you should see that when you're disabled MAF connector, you have an error 010 (and you can delete the error 009).
Measure resistance between white wiring on O2 sensor. Must by 2.5-5 Ohm. Else replace O2 sensor.
Ignition: check coil on cylinder 4 and 1, spark plug, ignition coil cap (see picture, ignition burn time for cyls)
PS: picture - throttle is opened, but IDLEsignal (idle speed mode) is active ( repair it! point 3.)
M16/6s2 is idle switch, see PDF
1. you car have AG4? (your ECU coded for AG4, Japan, KAT [000 019 128])
2. you have wiring diagram for HFM? if not have, download and print scheme 111.960 (it same)
3. you must check idle speed signal (ECU constantly sees (thinks) "idle mode" even when you hit the gas pedal) ).
disconnect "throttle connector", measure the resistance between pin 5 and 6. When the gas pedal is released - 0 ohm or 600 ohm when the gas pedal is depressed - infinite resistance.
If you have such evidence, the more you need to check wiring to ECU (see diagram). Perhaps a short to ground (minus).
ECU sees the 5V signal from the MAF.
you must disconnect the MAF connector and measure the voltage between pin 2-4 and between 2-5.
In both cases should be 11-13V (ignition on).
If you pass this test, I will write how to check the MAF (it will need to connect 2 wires).
As well you should see that when you're disabled MAF connector, you have an error 010 (and you can delete the error 009).
Measure resistance between white wiring on O2 sensor. Must by 2.5-5 Ohm. Else replace O2 sensor.
Ignition: check coil on cylinder 4 and 1, spark plug, ignition coil cap (see picture, ignition burn time for cyls)
PS: picture - throttle is opened, but IDLEsignal (idle speed mode) is active ( repair it! point 3.)
M16/6s2 is idle switch, see PDF
Last edited by hfmscan; Feb 20, 2017 at 03:44 AM.
Thread Starter
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Joined: Dec 2016
Posts: 76
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c200
wel thanks mike for ur reply
i have an hfm wiring diagram from WIS n i rewired the whole engine loom and the throttle body loom
i doubt the throttle body too the potentiometer brushes or may be a crack
i cross checked the values as in this vedio same results for me
and as i told you before alsoo i rewired the TB loom and im sure its accurate
i get voltages on both connector pins 2-4 and 2-5 , ANd my MAF is a brand new one bought from the company not even 4 months old
there was a intake backfire ! i removed the lambda sensor connector and aftre some time the backfiring stopped then and there i checked the o2 sensor its bad ! parts are order n waiting for it to get delivered
well the ignition timing period can it be the coil packs or is it the ECU ignition drivers BUX 127 VDO power switching transistor ? cause im having new coil packs as well ! n im having new HT leads also .
and yes i can see the PWM is less in igniiton time ! but what could be the problem
and yes i couldnt fix the idle M16/6s2 switch ! ill fix it !!
many thanks to you Mike and my other friend Russel !!
i have an hfm wiring diagram from WIS n i rewired the whole engine loom and the throttle body loom
i doubt the throttle body too the potentiometer brushes or may be a crack
i cross checked the values as in this vedio same results for me
and as i told you before alsoo i rewired the TB loom and im sure its accurate
i get voltages on both connector pins 2-4 and 2-5 , ANd my MAF is a brand new one bought from the company not even 4 months old
there was a intake backfire ! i removed the lambda sensor connector and aftre some time the backfiring stopped then and there i checked the o2 sensor its bad ! parts are order n waiting for it to get delivered
well the ignition timing period can it be the coil packs or is it the ECU ignition drivers BUX 127 VDO power switching transistor ? cause im having new coil packs as well ! n im having new HT leads also .
and yes i can see the PWM is less in igniiton time ! but what could be the problem
and yes i couldnt fix the idle M16/6s2 switch ! ill fix it !!
many thanks to you Mike and my other friend Russel !!
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c200
mike i recheck the voltages from MAF 2-5
i get zero 0 v
but 2-4 positive 11.43 v
my question is
connector pin 2 is a red/ blue wire which goes to fuse 23 (positive 11.43 with ground)
connector pin 4 goes to the right compartment ground the continues to ECU pin 22
connector pin 5 goes to ECU pin 27
connector pin 1 goes to pin 5 in ECU
so isnt the pin 1 and 5 are reference for the ECU ?
can the pin 2 and 5 give 11.43 ~ volts ?? confused
i get zero 0 v
but 2-4 positive 11.43 v
my question is
connector pin 2 is a red/ blue wire which goes to fuse 23 (positive 11.43 with ground)
connector pin 4 goes to the right compartment ground the continues to ECU pin 22
connector pin 5 goes to ECU pin 27
connector pin 1 goes to pin 5 in ECU
so isnt the pin 1 and 5 are reference for the ECU ?
can the pin 2 and 5 give 11.43 ~ volts ?? confused
Newbie
Joined: Mar 2008
Posts: 9
Likes: 3
mb
in the last month, I met this problem the third time.
you should check the wire between pin 5 (the MAF) and pin 27 (ECU connector 2).
If the wire is OK. you must remove both sockets of the computer and check the resistance between pin 32 (terminal 1) and 27 (ECU connector 2). It should be 0 ohms. If there is infinite resistance - you have to do the repair or replacement of the ECU ECU. As a workaround, you can try to connect the pin 5 to the body (minus), but I have not tried this solution
you should check the wire between pin 5 (the MAF) and pin 27 (ECU connector 2).
If the wire is OK. you must remove both sockets of the computer and check the resistance between pin 32 (terminal 1) and 27 (ECU connector 2). It should be 0 ohms. If there is infinite resistance - you have to do the repair or replacement of the ECU ECU. As a workaround, you can try to connect the pin 5 to the body (minus), but I have not tried this solution
Last edited by hfmscan; Feb 20, 2017 at 01:39 PM.
