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Pete
Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 25373
Experience:  Over 15 years experience as a Mercedes dealer technician
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1998 Mercedes Benz ML320, I get the Check Engine light,

Customer Question

1998 Mercedes Benz ML320, I get the Check Engine light, error code P0410, secondary air pump fail. Put 12v across pump, it runs. Checked across pump plug on cold start, 0v. Replaced fuse and relay, still 0v on cold start. Checked across pump fuse on cold start, 0v.
Help!
Submitted: 10 months ago.
Category: Mercedes
Expert:  Lou P. master tech replied 10 months ago.

Hello, the secondary air injection system can be tricky to diagnose ,what happens if you jump the relay terminals? instead of jumping the pump.

Customer: replied 10 months ago.
Hesatant to stick 12v into the relay, I also have no diagram of that circuit. But..pump runs on external 12v, but I NEVER get 12v at the pump plug, and I never get 12v at the fuse.
Expert:  Lou P. master tech replied 10 months ago.

ok i hear you, theres no worry though, let me get a diagram up.

Customer: replied 10 months ago.
I would love that
Expert:  Lou P. master tech replied 10 months ago.

ok what is your build date its on the drivers door sticker

Expert:  Lou P. master tech replied 10 months ago.

NM ok so its fuse 45 and relay K28 correct?

Customer: replied 10 months ago.
04/98 I have 2 K28 relays, same response from both. I only checked fuse F28, let me go check fuse 45, brb
Expert:  Lou P. master tech replied 10 months ago.

pins 1 and 2 of the relay are the ones that are activated by the ecm to turn the relay on, so you need to see if power is there on a cold start.

Customer: replied 10 months ago.
OK, fuse 45 is what I've been checking, 0v there on cold start
Expert:  Lou P. master tech replied 10 months ago.

ok so jump pins 3 and 5 on the fuse box where the relay goes, there is a diagram on the side of the relay and numbers on the bottoms of the pins

Customer: replied 10 months ago.
Looking at my relay... the coil power goes across pins 85 and 86..the smaller pins to the right and left of the large pin that is the opposite direction..
And what do I do?
Expert:  Lou P. master tech replied 10 months ago.

ok so take a wire with terminal ends and bridge the 87 and 30 terminals or the 3 and 5 terminals depending on the relay you have since you said it has a 85-85 that tells me it will be 87 and 30. you are pretty much going to jump power from 30 to 87 where the relay terminals would go into the fuse box

Expert:  Lou P. master tech replied 10 months ago.

im sorry i meant since you said it has 85 and 86

Customer: replied 10 months ago.
Ok terminals 1 and 2, which is the power to the relay coil. 0v NO power on cold start! I am NOT getting power to activate the secondary air pump.
Expert:  Lou P. master tech replied 10 months ago.

ok yes but now i want you to jump power from 30 to 87 to see if it will activate the pump

Expert:  Lou P. master tech replied 10 months ago.

are you able to do this tonight because i cant be on much longer and i would like to get your situation resolved

Expert:  Lou P. master tech replied 10 months ago.

ok i am going to opt out i wish you luck.

Expert:  Pete replied 10 months ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Did you still need help with this here?

Let me know so we can continue,thanks Pete.

Customer: replied 10 months ago.
Lou P. just got me in WORSE trouble!!! He wanted to have me jump terminals in the fuse box for the secondary air pump relay. In a rush to do this, I tried to put a cut off fuse pin in the relay slot for a connection..it did NOT work, and the pin fell into the fuse box!!!! Now I can't remove the pin...have tried super glue and my set of fine tweezers..nothing works.
So..the original problem persists...NO HELP FROM YOU!!!
And NOW I need instructions on how to remove the fuse box so I can clear the test pin I dropped in!HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Expert:  Pete replied 10 months ago.

Do you have the radio code as the battery will need disconnected?

Customer: replied 10 months ago.
Expert:  Pete replied 10 months ago.

Since the pin fell into the fuse panel you want to disconnect the battery to prevent any shorts from occuring first here.Below is the instructions on how to remove this fuse panel so you can remove the pin.Let me know when you get the pin removed so we can continue from here.

https://www.dropbox.com/s/owapzcpsavftulv/f-03-28.gif?dl=0

https://www.dropbox.com/s/k2jr9y2np5ilrkk/fu-03-28.gif?dl=0

Remove, Install 1 Open hood and raise to vertical position 2 Disconnect ground cable of battery CAUTION: To prevent unintended contact, insulate ground lead cable lug 3 Remove cover for fuses (1) NOTE: Installation: Check gasket for damage 4 Unscrew screws (3) and remove cover for control module section (2) NOTE: Installation: Check gasket for damage 5 Unscrew screws (4) and remove fuse and relay holder (5) upwards 6 Mark and disconnect electrical connectors to fuse and relay holder. NOTE: Connectors are fitted with mis-plug protection to prevent mix-ups. - Assignment and cable connections of fuse blocks 7 Detach electrical screwed connections to fuse and relay holder and remove fuse and relay holder 8 Remove injection system control module 9 Remove traction system control module 10 Unscrew screws (6) 11 Disconnect electrical coupling to blower motor/module box (M2/2) 12 Pull the wiring loom without separation point from the engine or major assemblies compartment with cable retainer out of the fuse and relay module (F1) and route the wiring loom back into the engine compartment. 13 Remove cover below instrument panel 14 Unhook control cable for hood release (13) from the operating lever and route cable outwards through the fuse and relay module 15 Unscrew nuts (8). 16 Disconnect electrical connectors and connections in the left footwell NOTE: This step involves all lines and wiring harnesses which run through the fuse and relay module and do not have a separation point inside the fuse and relay module. 17 Pull back wiring harnesses to the fuse and relay module 18 Unhook hoses for the windshield washer system from the brackets on the fuse and relay module 19 Remove windshield washer system reservoir 20 Remove fuse and relay module 21 Install in the reverse order