96 E300 P0403 code - PeachParts Mercedes-Benz Forum

Stihlindixie · #1 10-11-2015, 03:16 PM

I keep getting this code. I've checked the vacuum lines and have not found any issues. Once I clear the code I hear the EGR function the. Code throws again. I'm also not seeing the flap function right next to it. I know the flap under the cross tube is because you can hear it when you stand over the engine.

Not really sure what else to check.

tjts1 · #2 10-11-2015, 03:45 PM

Quote:

The Exhaust Gas Recirculation (EGR) system is controlled by a vacuum solenoid. The solenoid is supplied ignition voltage. The Powertrain Control Module (PCM) controls the vacuum solenoid by grounding the control circuit(ground) or driver The primary function of the driver is to supply ground for the object that is being controlled. Each driver has a fault circuit that the PCM monitors. When the PCM turns a component on, the control circuit voltage is low, or close to zero. When the component is turned off, the voltage on the control circuit is high, or near battery voltage. The PCM watches for these conditions, and if it doesn\'t see the proper voltage at the proper time, this code is set.

Read more at: OBD-II Trouble Code: P0403 Exhaust Gas Recirculation Circuit Malfunction
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Check the electric plug for the vacuum actuator.

Stihlindixie · #3 10-11-2015, 04:00 PM

Is that the plug that connects to the EGR?

tjts1 · #4 10-11-2015, 04:43 PM

No, whatever is feeding vacuum to the EGR. The system on the 96 is unique to that year so I have no idea how it look on your car.

Stihlindixie · #5 10-11-2015, 05:01 PM

I did find this line not connected. Not sure if it supposed to connect to this elbow or not. Over by the master cylinder.

Stihlindixie · #6 10-11-2015, 05:03 PM

Jeremy5848 · #7 10-11-2015, 06:50 PM

No, that's a bleed line (vent) for one of the vacuum solenoids. It's located there because the air behind the front firewall is supposedly a little cleaner. I put a little filter (small gasoline fuel filter) on mine.

The '96 E300 is smart enough to know if the vacuum solenoids, including the EGR solenoid, are not working. You can test the EGR system by blocking the valve with a solid gasket but the electrical connection must remain in place. Later models are even more sophisticated and can tell if air is flowing through the EGR valve!

Additionally, the "throttle" flap in the intake pipe just before the EGR valve is partially closed by the EGR system to reduce the air pressure in the intake so that more dirty exhaust is sucked into your clean engine (diesels normally run with intake wide open so little or no intake manifold vacuum). The '96 E300 has a pressure sensor at the rear of the engine compartment (driver's side) connected by a rubber tube to the intake manifold. When the throttle flap is told to close down, the sensor should see a drop in air pressure; if not, a code like the one you're seeing is set.

Jeremy

Stihlindixie · #8 10-11-2015, 11:29 PM

Quote:

Originally Posted by Jeremy5848

No, that's a bleed line (vent) for one of the vacuum solenoids. It's located there because the air behind the front firewall is supposedly a little cleaner. I put a little filter (small gasoline fuel filter) on mine.

The '96 E300 is smart enough to know if the vacuum solenoids, including the EGR solenoid, are not working. You can test the EGR system by blocking the valve with a solid gasket but the electrical connection must remain in place. Later models are even more sophisticated and can tell if air is flowing through the EGR valve!

Additionally, the "throttle" flap in the intake pipe just before the EGR valve is partially closed by the EGR system to reduce the air pressure in the intake so that more dirty exhaust is sucked into your clean engine (diesels normally run with intake wide open so little or no intake manifold vacuum). The '96 E300 has a pressure sensor at the rear of the engine compartment (driver's side) connected by a rubber tube to the intake manifold. When the throttle flap is told to close down, the sensor should see a drop in air pressure; if not, a code like the one you're seeing is set.

Jeremy

Thanks for the info. I'm also getting P0400. When I ckear the codes it works but only for a second. I found that sensor. I'm just not sure what to do next.

Jeremy5848 · #9 10-12-2015, 12:08 AM

I don't know if that sensor is simply a switch or if it is more complicated. Let me look at my '96 and you make sure the hose from the intake manifold to the sensor is good and that the throttle flap in front of the EGR valve is working.

pimpernell · #10 10-12-2015, 12:43 PM

Quote:

Originally Posted by Stihlindixie

Thanks for the info. I'm also getting P0400. When I ckear the codes it works but only for a second. I found that sensor. I'm just not sure what to do next.

The throttle position sensor error code can have a multiple causes. There are a number of sensors that work in combination with one another which can cause this code besides the "throttle position sensor" itself. which is located adjacent to the firewall, drivers side.

There is a small black sensor connected to the intake manifold atop the driver side wheel well.

There are two other sensors located on the side of the air intake filter box. Both of these sensors have the same part number. One controls the resonance flaps, and the other controls the EGR valve.

On the underside of the intake manifold, there are two vacuum devices that control the resonance flaps.

All these sensors are all connected by small rubber vacuum lines, that can spring a leak and cause a code, so I would check those out the vacuum lines themselves first.

The second thing I would do is disconnect all the electrical plugs to each sensor one at a time, and spray each one with electric contact cleaner, and re-attach. Good luck!!
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tjts1 · #11 10-12-2015, 12:48 PM

Thats not a TPS error code.

pimpernell · #12 10-12-2015, 04:06 PM

Quote:

Originally Posted by tjts1

Thats not a TPS error code.

I realized that, but that system of sensors all seem to be interrelated, and I thought that the information provided might help him find his problem. Those two sensors on the side of the intake filter box might be related to the P0400 error.

Stihlindixie · #13 10-15-2015, 03:45 PM

Come to find out it's the EGR itself acting up. My MB tech recommended replacing it but to look for a used one due to the cost of a new one. The new part prices are insane for one BTw, but not having any luck locating a used one.

Jeremy5848 · #14 10-15-2015, 04:13 PM

Quote:

Originally Posted by Stihlindixie

Come to find out it's the EGR itself acting up. My MB tech recommended replacing it but to look for a used one due to the cost of a new one. The new part prices are insane for one BTw, but not having any luck locating a used one.

Do you mean the EGR valve itself or the electronics?

Stihlindixie · #15 10-15-2015, 10:02 PM

It's the EGR itself. All the electrics checked out.