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Warm restart in limp mode - 2001 V70 T5

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volvolugnut
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Warm restart in limp mode - 2001 V70 T5

Post by volvolugnut » Mon Aug 12, 2019 2:15 pm

I have been trying to troubleshoot a problem with 2001 V70 with T5. About 6 times over 6 months time (about 2000 miles) I have had a problem when I start the engine. It immediately stumbles and idles rough. I can only keep running by giving partial throttle and will only rev to 1700 or 2500 RPM. If I can keep it running, I have crept home a few miles in this state. I believe it is in limp mode. A couple of times it 'cured itself' in about a mile. Every time it has restated fine after setting for a couple hours - even on 100 degree days.

Each time has been a restart after the engine is warmed. Never occurred at a cold start over night or setting for several hours. First 2 times were in 50 degree clear weather and last 4 times in 80 to 100 degrees.

This car has 197,000 miles and has seen mostly short trips on the last 50,000 miles in 8 years. It is in good mechanical condition and had XeModex electronic throttle replacement at 179,000 miles.

The last 3 times I have used Autophix scanner to read codes: CEM-DF13, ECM-902A, CEM-DF16, ECM-903F,CEM-1A5D AND ECM-4010. Best I can tell, these codes point to a short to power failure in the ETM wiring. The ECM-4010 is a long standing fuel tank vent issue that does not seem related to the other codes. There were a couple other codes that only occurred once: CEM-1A5F, CEM-1A61, CEM-1A62 and BCM-0065. I think these may be codes caused by the main 6 codes.

Since these problems started, I have recently cleaned the throttle plate - it was not very dirty. I replaced the battery - it was weak and old. I have cleaned the Plus power cable at the under hood cable end - not badly corroded. I have confirmed good voltage stopped and running at the front fuse box. Once, while in limp mode, I removed and replaced #7 fuse for ETM and did not hear the ETM buzz and then click in a few seconds.

I have been trying to get the problem to occur when sitting at home, but have not been able to get a failure to repeat in semi controlled conditions. I am currently removing wiring wrap on the fuse box to ETM to ECM to look for wire insulation failure.

I have read that 2004 models had a problem with overheating CEM under the dash. I suspect this might also be a problem on high mileage 2001 V70s in the southwest. This car has spent most of it's life in warm climate so has many thermal cycles on the CEM, ECM and TCM.
I have learned that the 2001 to 2003? V70s have air duct from the cabin to the ECM/TCM box under hood in front of right fender. When the AC in on cold and fan on high, there is a slight flow of cool air out the front of this box. One Volvo source called it the 'cool box'.

I have read several threads on this and other Volvo forums of similar random stalling problems in 2000-2005 Volvos. Most do not include a solution to the problem. A couple (2004 models) reported some success adding computer heat sinks to the CEM and adding fan to blow on the heat sinks.

Have others had similar resolved or unresolved problems with these models? Has time and miles created a new failure mode? Ideas?

volvolugnut



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abscate
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Re: Warm restart in limp mode - 2001 V70 T5

Post by abscate » Tue Aug 13, 2019 3:58 am

The heat sink on CEM in hot climates is a known issue and worth exploring. I’ll try To find good threads


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volvolugnut
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Year and Model: 2001 v70
Location: Midsouth USA
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volvolugnut

Re: Warm restart in limp mode - 2001 V70 T5

Post by volvolugnut » Tue Aug 13, 2019 5:46 pm

Update:
I have also replaced the Engine Management (also called ETM) relay and cleaned the cabin air filter. Relay was replaced before the last failure.
Today I opened the wiring harness between ECM and the engine fuse box. Access is poor, but this can be done with air ducts and radiator fan removed. The wires along the bottom on the left side were very dirty, but I have not found any insulation damage yet. Still some portions to open harness and examine.
I have a tool for ECM and TCM removal to arrive in a couple days. I will then check the condition of contacts for the ECM and TCM in the enclosure box.



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