C70 ECM electrical puzzler

[RexxWonder]

OK. Thanks for all the good ideas...so far I'm still stumped. I do have some new info to add:

When I start the car first time, it will run for 4-5 minutes and then shut down on its own. After that, no more spark until the next day.
One of the consistent error codes is -ECM-720A: Immobilizer communication - signal missing-
-Does anyone know if the Immobilizer has some initial period where it allows the car to start while it looks for the proper info or signal?
-Could the immobilizer be looking for the code for some initial period and then shutting down when it isn't found?
-or should I look for a short in that communication line from ECM to immobilizer?
-Logically, can this explain the other codes lighting up? (I'm thinking that once the engine dies, the ECU isn't getting any Cam or Crank sensor info since they aren't turning).
-Also, I have to charge/jump the battery every morning as it drains completely overnight.

I have searched the entire front of the engine compartment within range of the a/c hose and can see no obvious breaks or damages from this.
I have unplugged the high-pressure sensor to the a/c but still no differences. This is so frustrating because I only have a 4-5 minute window to try and trouble shoot while the car is running...then I'm dead until the next day.

Any new ideas or pointers to how the immobilizer works are greatly appreciated.

[abscate]

Just turn on ignition and trace that current fault first. Maybe refrigerant has torched your alternator or regulator on back of the alternator ??

The immobilizer will shut off the car in about 3 seconds. Obviously you have major wiring issues

[precopster]

Have you investigated the a/c hose damage?

The immobiliser cuts power to coils, throttle and crank/cam sensor.

Clean the antenna ring connector or replace it preferably. The transponder in key check is continuous while engine is running.

[RexxWonder]

Hello all,

I am still working on and thoroughly befuddled by this problem. If you have followed my thread, you will see that I have a very strange problem. I have done more elimination and have some new info to add:

-Car starts fine when completely cold...first time, every time
-After about 3 minutes it will stall if idling
> If I sit in the car and keep the accelerator down when this issue starts (~ 3 minutes), then the car will still run, but VERY poorly:
sputters and jumps, but will continue to run.
-I have replaced the temp sensor, cam and crank position sensors, fuel filter and fuel pump.
-Today I unplugged the Temp Sensor to see if that made any difference (since it seems to be somehow temperature related). It made no difference. Still stalled at about 3 minutes (or when the temp gauge is about 3/4 way to running temp).

So, to recap, here I am:
Car starts and runs fine on the first start of the day
after 3 minutes (or 3/4 temp) will stutter and stall if accelerator isn't depressed. Still run very rough and undriveable.
Fuel pressure is good
Spark is good.
Will not start again until the next day.
-Also, battery drains every night.

No codes at first start. No check engine light. Once it dies it will give me communication codes and ABS, but nothing obvious.

So, I am starting to lean towards some issue with the Throttle Control Module? Maybe the butterfly stuck? I have not yet tried to clean it. Could it be that simple? I might shoot myself if this turns out to be the issue.
Stay tuned.

[jonesg]

" -ECM-720A: Immobilizer communication - signal missing-"

Thats the consistent code, there are no codes about throttle module.
I find when it says signal missing it just as often translates to voltage missing, unplugged sensor , blown fuse etc.

[sleddriver]

So, to recap, here I am:
Car starts and runs fine on the first start of the day
after 3 minutes (or 3/4 temp) will stutter and stall if accelerator isn't depressed. Still run very rough and undriveable.
Fuel pressure is good
Spark is good.
Will not start again until the next day.
-Also, battery drains every night.

If the battery drains everynight, then you have to charge, then equalize, before starting the next day? Over & over?
My 98 has a very different electrical system. However, a battery drain such as yours can be traced to a faulty ckt. Time to hook up an ammeter and start pulling fuses.

Since IMMOBI is mentioned, do you believe this to be the cause of the behavior or just a possible?

Since you're in Austin, call Vol-Tech or Swedish Auto and have them take a look.

[RexxWonder]

Thank you all for the input.
As for IMMOBI, no. It would not start on such a consistent basis if that were the problem. There is definitely a "ghost in the machine". I removed the ETM last night and am cleaning it now, but it wasn't as obviously dirty as I was hoping.
There is such a definite pattern to this issue that it seems I could find it logically. But the VIDA/DICE is of no use in this instance as the car runs fine when it starts and there are no codes (other than the convertible top out of sync). There is good spark and plenty of fuel pressure. I have come to feel it must be an issue with the lean/rich status of the fuel. There must be a trigger point in the temperature curve that tells the ETM to open the butterfly and/or change the fuel/air ratio and this is not happening. I just have been unable to find anyone with the knowledge who can help.
I have taken it to a local "Swedish Motors" mechanic, but they want to run through all the same scenarios that I have already covered and won't discuss the "logic" of the issue with me.
The ETM issue makes the most sense to me now...it fits all of the symptoms logically and chronologically (when the a/c hose blew off, it spewed coolant and oil straight up onto the ETM). Either cleaning it will help, or I may have to try rebuilding it with a XeMODeX hall-effect. I just wish there were some way to be sure that this is the problem. This is the maddening issue with me. I have a 2001 Audi A6 and the VAGCOM diagnostics will tell em any and everything about the car. I can be positive of the issue before ever breaking under the hood. This F***ing Volvo is driving me crazy because I only have ~3 minutes of run-time per day to try and diagnose the issue. AUGH!

[sleddriver]

Call Vol-Tech. Somethings FUBAR.

The engine doesn't have to be running to trace the battery drain issue. I'd go after that as you may discover the answer for multiple problems.

Still puzzled an A/C hose could blow up like that. Weird...very weird.

[abscate]

Once you have the no start , you have to diagnose spark and fuel and find out what is missing. I would start by solving the drain first, and the first stop there is the voltage regulator on the rear of the alternator
How old is the battery? That full cycling will kill it in a week or so, and bad supply voltages will mess up a CANBUS car pdq.

[precopster]

Unplug ETM and see if battery still drains. I'll doubt it's the culprit.