Help with ECM fault code P048000, fan 1 control circuit

[Lowflyer20]

So I'll start by stating I only have some basic mechanical knowledge, and better than average low voltage electrical experience. This actually happened a few months ago, so my memory is a little foggy as to the exact order I performed things and what trouble codes showed up, and when. Here's the conundrum:

My girlfriend has a 2010 Volvo S80 T6 AWD. One day her car is dead, so I jump start it and notice that the cooling fan is running right away, but I let the car run until the battery is fully charged again. When I turned off the car, the lower right cooling fan (orientation while seated in the driver's seat) ran continuously, well beyond any expected run time with a warm engine after it's shut off. I don't have VIDA / Dice, so only OBDII testing was performed with a pretty generic tester. I was getting several codes, including an indication that the vehicle would fail a SMOG test, so now I'm hunkering down for several projects on this car. Because I planned on doing some more in depth work on this vehicle and some others I own, I decided to get a more robust diagnostic tool, the Autel MaxiCOM MK808BT.

Whatever code(s) showed up the first time, with the generic tester, made me believe the fan control module was the likely culprit, but I also saw codes for the engine coolant temperature sensor. I disconnected the battery to prevent a repeat and began doing my DIY research via Google.

About an hour later I reconnected the battery and the same fan started running again. I disconnected the battery again, unplugged all three connectors from the module, then removed the module. With the module out of the engine compartment I could easily hookup my voltage tester. I reconnected the battery and found that there was continuous voltage to the plug that ran that particular fan. In my mind, problem identified, replace the fan control module.

I ordered a new fan control module and thermostat at the same time, since the coolant temp sensor is part of that component. When I received the OEM replacements, I removed the thermostat and found it was all broken with the spring sitting loose in the cavity. Then I plugged in the new fan control module and tested it with my voltage tester. No continuous voltage like on the old one. I swapped it out and, Voila! No more continuous running fan. I tested at the OBDII with the original tester and cleared the codes.

At this point I no longer see any code for the coolant temp sensor, but the ECM P048000, Fan 1 control circuit code shows up. It seems that the different diagnostic tools have varying success with clearing codes, so I clear the code with the Autel. Run the diagnostics again and the same code appears. I needed to do the drive test to clear the O² sensor issue for SMOG testing, so I drove around a good half hour, which also included cycling the ignition on and off. I figured that would be plenty of time in case that was needed to clear the P048000 code as well.

When I got back I cleared the P048000 code again, then removed the dongle from the OBDII port, so I could establish a new connection. Code still appears.

My limited mechanical knowledge still forms the theory that once the thermostat took a crap, it was obviously not regulating the engine temperature any longer, which likely contributed to making the cooling fans run longer causing the fan control module to fail, right? FYI - my girlfriend said no warnings ever popped up in the cluster to indicate the engine overheated.

With both of those components replaced I would think I could get that damn code to stay cleared. What else might I be missing, or need to replace / repair? Does the number of start and stop cycles of the ignition have any bearing on clearing various fault codes?

Any help would be much appreciated.

[pbierre]

To get help with a DTC, give us the exact wording the Autel gives for a P048000.

When a thermostat breaks up internally allowing coolant to flow unrestricted, there is no overheating condition. You'll instead have startup underheating -- it will take longer for the engine to come up to temperature.

[RickHaleParker]

2010_S80_Cooling_fan.gif (22.69 KiB) Viewed 15864 times

ECM-P048000 Fan 1 Control Circuit. General Failure Information. No sub type information, B6304T2

Diagnostic trouble code (DTC) information ECM-P048000

Condition
The engine control module (ECM) sends a signal (speed request to the cooling fan) to the cooling fan module. The cooling fan module then regulates voltage to the fan motor at an infinitely variable rate. The diagnostic trouble code is generated if the engine control module (ECM) detects that fan speed is low.

The diagnostic trouble code can be diagnosed when the engine is running.

Note! The electric cooling fan may have a post-running time of up to approx. 6 minutes after the engine has been shut off. The time for the electric cooling fan's post-running depends on the engine's temperature, temperature in the engine compartment as well as the pressure level in the AC system.

Substitute value
Nothing.

Possible source

• Internal fault in the electric cooling fan.
  Short-circuit to supply voltage in the signal cable.
  Damaged cooling fan module.

Fault symptoms

• Overheated engine.
  Electric cooling fan does not operate

[pgill]

I own a S80 but I’ve never had this problem.

Let me try to explain what I would look into.

To measure the amount of Current flowing into a circuit you can put a resistor in series and measure the Voltage drop across the resistor.

Typically when this is done the resistor has a low value so that most of the voltage gets to the device that the circuit is powering (a fan motor in this case)

This may come as a surprise, the Fuse for the Fan is a resistor just like what I described.

And based on what I read the ECU is using the Voltage drop across the fuse to confirm how much power is going to the fan.

I would look at the fuse contacts and get a new fuse if it was my S80

Take a look at this link for more information

viewtopic.php?t=88413


Good luck


Paul