Odd Electrical Behavior 2001 V70XC

[Firebirdracer82]

Hi Matthews Volvo Site!

I'm new to the volvo world, but not to cars. I picked up a 2001 V70XC wagon with a strange electrical gremlin.

What the car is doing:

I got the car from a shop and an owner that couldn't get it to start. Took it on as a project to get back on the road.

Car is a crank, no start. All other systems work (climate, radio, wipers, windows, etc)

If you let the car sit all night, it will start and run. If it shuts off, then it will crank but not start until the next day. (I leave the battery unhooked)

What I have been doing:

In the morning, before I have started the car, a (not volvo) scanner will communicate with the ECM. When it can read the ECM then the car will start.

After it either shuts off or is turned off, you cannot read the ECM from the bi-directional scanner. It's like it has gone offline.

At one other point, the bi-directional scanner was reading the RPM through the TCM and it would either be 6000 or 0, showing the engine running when it's not.

I have tried unplugging the MAF - no change.
I have unplugged the ABS - no change
I have tried going through all fuses. Nothing that's not firing up.
I have tried to retrace the CAN bus but have not OHmed them out yet.

I have not checked all grounds - that's kind of a tomorrow project.

A Clue:

When the car first started, I had the CEM out and dangling. Car was running for ten minutes (running well). I got in it and my foot grazed the CEM and the car shut off.

So, where do I start?

I think the ECM is probably good since I can see it in the mornings before I start it, but maybe it has a wiring fault.
The CEM might be something viable to replace/recondition.
Since it starts in the morning, I am also assuming that the ring lock and key is recognizing.

So what do I do first?

[RickHaleParker]

Sounds like something is temperature sensitive.

I would:
1. Take pictures so you can get all the shunts back in the right place.
2. Remove the shunts. ( They look something like big black fuses )
3. Remove the CEM from the fuse box assembly. ( The actual CEM is shaped like a paving brick. )
4. Clean all the electrical connectors and check them for damage.
5. Reassemble using your pictures.
Test it to see if it made a difference.

[Firebirdracer82]

Here is an update on what I have done, and the results:

1.) Pulled CEM, Cleaned all points with Electrical Contact Cleaner. I did not see anything abnormal other than very very slight corrosion. I do not have a method to further test the CEM.

2.) Pulled the ECU and visually inspected it. There were no burnt pins or dark spot on the board.

3.) Cleaned grounds on driver's side fender - They looked OK, but never a bad idea to clean a ground!

4.) Looked at rear fuse box (the 40s) and it did have some corrosion around it. I tested all fuses for resistance and measured .6 evenly. Cleaned them and returned them. Also cleaned the bus bar on that box.

5.) Recharged battery.

ECM Codes I pulled this morning when I could use my code scanner on the ECM:

ECM-1600 - Boost Pressure Signal too high/too low

ECM 8410 - 5 volt power supply, signal too high/too low

ECM 1000 - Control Module signal too high/too low.


Behavior this morning:

It started for a brief time, and then stopped. Then I disconnected the battery and did the work above.

Placed the battery on charger.

Was able to start it again a few hours later, have it run, used it to back up and pull forward, then died again. Crank no start condition continues.

Also, one thing I can say, is that when the RPM needle moves, then the car will start. If it doesn't move, then the car won't start. I have swapped crank position sensor, but I am thinking this is a power to ECM problem or an ECM problem.

Thesis:

I think that the computer is bad or some portion of the CAN network is overloading the system so it cannot communicate. However, even when I cannot communicate with the ECM, I can always communicate with the TCM, so I don't know that it's the network.


Thank you for the suggestions and anything where I can go from here.

[matthew1]

Welcome to MVS, Firebirdracer82.

5.) Recharged battery.

...

Placed the battery on charger.

What's the volts reading with a multimeter at rest? While running? How old is the battery?

[Firebirdracer82]

Battery is fully charged and new as of May this year (stole it out of my XK8). Scanner has showed it charging when running but I have not used my multimeter on it yet (been trying to do other tests in the shorter times it's running but will follow up on this next time it is up).

This afternoon I pulled the Boost sensor connection and the AC High Pressure Switch connector as well. No change in condition as of yet. Also pulled the boost sensor without a change and replaced. Have the ABS pump plug off as well.

Codes I was able to pull from the ECM, cleared, and reappeared with some new codes:

ECM-1600 - Boost pressure Sensor (unplugged)

ECM 8410 - 5 volt power supply too low/too high

ECM 3100 - Engine Speed Sensor (signal missing) (New Code)

ECM 1000 - Control Module Signal too high/low

ECM 3000 - Camshaft position sensor signal too high/low Camshaft position sensor fault signal.

[RickHaleParker]

1. Don't guess at voltages. Measure then with a Volt meter.
2. It does not take much corrosion to cause problems.

**********************
ECM 8410 - 5 volt power supply too low/too high. That the one that concerns me the most.

Common Causes

1. Shorted Sensor: A failing external sensor connected to the 5V rail can pull the entire reference voltage down or short it to a higher voltage.
2. Corrosion or Bad Wiring: Damaged wire insulation, corrosion on the CEM connectors can cause voltage drops or spikes.
3. Weak Battery: A degraded or failing car battery can destabilize internal module reference voltages.
4. ECM Failure: A damaged internal voltage regulator or shorted internal component (like a MOSFET) inside the CEM itself.

There are 5 sensors on that 5V rail. they are:

1. Mass Air Flow (MAF) Sensor
2. Boost / Manifold Absolute Pressure (MAP) Sensor
3. A/C Pressure Sensor
4. Engine Oil Level Sensor
5. Fuel Tank Pressure Sensor

1.Unplug one of the five sensors one at a time.
2. Clear codes.
3. See if ECM 8410 comes back.
4. Repeat 1 -3 until you found a sensor that is causing ECM 8410 or run out of sensors.
5. If you run out of sensors. Unplug them all. Clear codes, See if ECM 8410 stays away.

Notes: CEM 5-volt reference signal is pin A39 (a Violet-White wire found on the black side of the CEM).

[Firebirdracer82]

I ran the car this morning with no scanner and here his what happened:

Boost sensor unplugged, MAP sensor unplugged, ABS unplugged, AC sensor unplugged.

Have not taken off fuel pressure sensor.

Car started and immediately ran for three to five minutes before shutting down.

In that time, I measured the battery voltage, before and after it started.

Before starting - 12.24V

Running - 13.53V

After it got to about 25% operating temp, the car shut off.

I am suspecting that there is a bad solder connection or wiring fault with the ECM itself but I wanted to see what people believed before I took that step and sent it off to be replaced.

I hav cleaned the main grounds, the drivers fender grounds, the battery grounds, the rear bus connector and fuses, cleaned the CEM and noted no problems.

It appears that this problem only occurs when the engine has been running for 3-5 mins so I am assuming it has something to do with heat in the electrical system.

What are your thoughts? I will report back with the solution regardless (as a hate threads that end early)

[vtl]

How old is the upstream oxygen sensor? What you describe is car dies when ECM switches to closed loop and uses HO2S data. First few minutes ECM uses software tables for air-fuel mixture, then it switches to the sensor.

[jonesg]

I've been reading volvo forums for 10 yrs and can't recall an ECM problem, the odds are toward the CEM.
Something is sending corrupt data triggering the ECM to shutdown.
VIDA can monitor several parameters at the same time, short of that I'd send the CEM to Xmodex for testing.

It can also be oddball stuff like clogged cat or massive vac leak, such as this video.
Although that doesn't explain the loss of OBD port access.

[Firebirdracer82]

VTI, as for upstream O2, I have no idea. Took this car on as a project that the dealership couldn't diagnose and I love a challenge, it keeps me occupied. Jonesg, I can kind of agree with the idea that corrupted data is flowing, but I might try the ECM first.

Here is why:

I think I have isolated it as an ECM problem with ice.

I did this by cooling the ECM with an ice pack for approximately 15 minutes and the car would start, after being given a time to cool down. It would run for 2-5 minutes, then shut off. I would let it cool down with the ice pack and it would start again after another 15 minutes.

To be clear, the car had NEVER started multiple times during the day - this was a first due to cooling the ECM with an ice pack for fifteen minutes after it shut off. Communication with the ECM was also restored during this time, but fell out when the car stopped.

I put the CEM back in the holder under the dash and it still did the same thing. Repeated this process 5 times and 5 starts.

So, I am assuming that this is my issue. Will report back when I have a replacement ECM installed. It could of course be the O2 causing a short and shutting down the system, but I think it more likely the ECM due to the icing it down.