Open circuit code, so maybe look for an open circuit.

Brett

 

Thanks, never thought of that.
Open circuit most often means component failure. That is why I replaced the pump.
What I was asking for was if anyone else had this problem and it wasn't the pump and knew the next common failure point so I wouldn't have to go on a snipe hunt.
I just looked at the connector that is under the rear passenger seat and it looks fine.
When I have light and heat I'll pull the seat back and trace it back to where it transitions from interior body to exterior and look for signs of damage. I doubt I'll be able to see anything undercar as it is on top of the fuel tank as best I can tell, what I could see when I replaced the pump looked ok.

 

Ok, that's strange. One of the pictures of the heat shield got marked as sensitive content.
Can one of the Mods fix that?

 

Super disappointing. That's a lot of work that I was prepared to do to eliminate our issue. Watching to see how you ultimately resolve. Thanks for the pictures to document!

 

Feel for your troubles, Dave. Apologies if this has already been covered but did I read somewhere on this forum that there's a software update which takes into account the age of the LDP and reduces the sensitivity of the parameter which throws the CEL? Hopefully this isn't something I'm just imagining in my head.

 

That would be awesome if it's true!

 

Looking in VIDA under generic and Volvo OBD codes I did not find any for P2400. I am not saying that code is not there, just saying that I can not find a reference for it. Check fuse 11B5 under the hood. 6/67 is the LDP pump.
Erase the code and do a battery cable reset. The code should not return until the ECM has run an evap leak test.
The evap test will run when the ECM decides to run it. It might be at 2am. The new 2006 ECM SW logic has changed.
The ECM relies on amp draw of the LDP. There is a high limit and a low limit, out of this range, it sets an evap code.
The old logic just ran the test, it did not take into account for LDP wear. A failing LDP would set an evap code. The new 2006 SW logic will run the LDP to get a base amp draw and then start to run the test. The LDP pulls a minor vacuum on the fuel tank system. As the vacuum pull increases the LDP amp draw increases. The ECM knows the fuel level ect and knows about how long the test should take. A cracked line for evap, not fuel pressure, to a missing gas cap, none or very light amp draw and a code is set ect. The signal too high or too low has to do with amp draw when running the evap test. You did the right thing in replacing the LDP. They all almost seem to fail at least once. You have the updated LDP. The old original LDP's were all black plastic. You do not need the updated ECM logic for the evap test to run, but it will not do a LDP base test either. The below codes are generic and Volvo.

 

Looking in VIDA under generic and Volvo OBD codes I did not find any for P2400. I am not saying that code is not there, just saying that I can not find a reference for it. Check fuse 11B5 under the hood. 6/67 is the LDP pump.
Erase the code and do a battery cable reset. The code should not return until the ECM has run an evap leak test.
The evap test will run when the ECM decides to run it. It might be at 2am. The new 2006 ECM SW logic has changed.
The ECM relies on amp draw of the LDP. There is a high limit and a low limit, out of this range, it sets an evap code.
The old logic just ran the test, it did not take into account for LDP wear. A failing LDP would set an evap code. The new 2006 SW logic will run the LDP to get a base amp draw and then start to run the test. The LDP pulls a minor vacuum on the fuel tank system. As the vacuum pull increases the LDP amp draw increases. The ECM knows the fuel level ect and knows about how long the test should take. A cracked line for evap, not fuel pressure, to a missing gas cap, none or very light amp draw and a code is set ect. The signal too high or too low has to do with amp draw when running the evap test. You did the right thing in replacing the LDP. They all almost seem to fail at least once. You have the updated LDP. The old original LDP's were all black plastic. You do not need the updated ECM logic for the evap test to run, but it will not do a LDP base test either. The below codes are generic and Volvo.

View attachment 174199


View attachment 174198

I just did a quick check and the fuse is good. My car seems to run the test within a few seconds of starting. I can clear the codes and then start it and it will have the code once, shut it off and restart and it will pop a second code and turn on the MIL.
I have already done a battery reset with no change.

 

Plug ends? Like the part that connects into the pump? Did you clear those with electrical contact cleaner? There might be crud in there causing a short?

 

The LDP runs a pressure test not a vacuum test.
The 2004 and 2005 LDP PDF's explains in more detail about how the LDP test is run.
The evap test will only run after the engine has been turned off as noted in the PDF's.
I assume that the code is not clearing out because the ECM sees something that is not in spec.
Did the connector click and lock into the LDP?
With the engine running do you have 12 volts on the Green-Gray wire of the LDP connector?
I am not sure if the LDP Pin 4 Green-Gray wire from 2/143 CEM relay is a ground or 12 Volts.
Relay 2/143 may have failed.
ECM B:40 and B:7 grounds the 6/67 LDP.

.



Leak diagnostic unit (certain markets only)
The function of the leak diagnostic unit is to pressurize the fuel tank system during leak diagnostics and to open the fuel tank system to the surrounding air during evaporative emissions control.

The leak diagnostic unit consists of a plastic housing with:
1. electrical air pump
2. a valve / solenoid which governs the air flow in the unit
3. a heater element (PTC resistor) which warms up the pump.
The electrical pump, valve and heater element in the unit are supplied with voltage by the system relay. The pump, valve and heater element are grounded (control) in the engine control module (ECM).
During leak diagnostics the pump in the leak diagnostic unit starts. The valve in the unit is operated by the engine control module (ECM) by grounding the different circuits internally in the engine control module (ECM). The engine control module (ECM) gauges the power consumption of the pump during pressurization. The power consumption corresponds to a certain pressure in the fuel tank system.
The engine control module (ECM) can diagnose the leak diagnostic unit.
The valve in the leak diagnostic unit can be activated and the power consumption of the pump can be read off using VIDA.
The leak diagnostic unit is at the upper front edge of the fuel tank.

 

The LDP runs a pressure test not a vacuum test.
The 2004 and 2005 LDP PDF's explains in more detail about how the LDP test is run.
The evap test will only run after the engine has been turned off as noted in the PDF's.
I assume that the code is not clearing out because the ECM sees something that is not in spec.
Did the connector click and lock into the LDP?
With the engine running do you have 12 volts on the Green-Gray wire of the LDP connector?
I am not sure if the LDP Pin 4 Green-Gray wire from 2/143 CEM relay is a ground or 12 Volts.
Relay 2/143 may have failed.
ECM B:40 and B:7 grounds the 6/67 LDP.

.



Leak diagnostic unit (certain markets only)
The function of the leak diagnostic unit is to pressurize the fuel tank system during leak diagnostics and to open the fuel tank system to the surrounding air during evaporative emissions control.
View attachment 174263

The leak diagnostic unit consists of a plastic housing with:
1. electrical air pump
2. a valve / solenoid which governs the air flow in the unit
3. a heater element (PTC resistor) which warms up the pump.
The electrical pump, valve and heater element in the unit are supplied with voltage by the system relay. The pump, valve and heater element are grounded (control) in the engine control module (ECM).
During leak diagnostics the pump in the leak diagnostic unit starts. The valve in the unit is operated by the engine control module (ECM) by grounding the different circuits internally in the engine control module (ECM). The engine control module (ECM) gauges the power consumption of the pump during pressurization. The power consumption corresponds to a certain pressure in the fuel tank system.
The engine control module (ECM) can diagnose the leak diagnostic unit.
The valve in the leak diagnostic unit can be activated and the power consumption of the pump can be read off using VIDA.
The leak diagnostic unit is at the upper front edge of the fuel tank.

I believe I have an electrical fault and not a fault with the system function, e.g. a problem with the wiring or the voltage to the pump, not of that working of the pump or the lines.
I'll get to dive into it on T-day and see what I can come up with.

 

Have you verified proper functioning of the evap system leak test? I'm assuming you have a bi-directional scan tool. If not, I highly recommend getting one. Manually command the pump to run and monitor the current draw as described in the Volvo docs posted. Question #1, does the pump run? If yes, then Question #2, does the current draw curve look reasonable?

The Volvo docs say the computer acquires a reference current for a known leak. It's not clear how you find out what that reference current is. Maybe by just observing the LDP current draw with the scan tool and catching it when it's running the reference test.

Brett

 

Well, the problem was mouse damage. The wires exit the body at the access panel for the fuel pump and right there one wire was gnawed through. I guess the wire was 9 10ths gnawed through and it finally broke.
I did an overlay but at some point, I want to get a replacement harness. There is a plug under the back seat and of course the other end is at the pump. So, some car is going to donate an intact harness to me.

Of course nothing comes without a price. I reconnected the battery and started the car to see if I would get a code but I forgot that I had unplugged the rear seatback. It has an orange plug that goes to the seatbelt pre-tensioner. So now I have an SRS service light.

Can VIDA turn off the warning?

 

Well, at least now you know. That sucks but at least you finally have the answer.

Regarding SRS, I just replaced my steering wheel (repeatedly) and can confirm that VIDA can indeed reset SRS lights

 

Nice work. Good to see the fault code was spot on.

Brett

 

"New" harness for $9.10