2005 S60 short in 5-volt power supply cable?

casbah99 · Post by **casbah99** » 05 Nov 2014, 08:55

Hi, I'm wondering if anyone can give me any advice on how to fix a problem I'm having with my 2005 Volvo S60 2.5T.

The engine misses. If I can get it to drive and get out on the road, the missing improves but it's still rough. I'm currently charging the battery overnight.

My VIDA diagnosis gives me these major faults:

ECM-810D 5 volt power supply. Signal too low
ECM-126B Boost pressure sensor. Signal missing
ECM-121D Mass air flow (MAF) sensor. Signal too low
ECM-290D Fuel pressure. Signal too low

The boost-pressure sensor and the MAF sensor both plug into the same bundle of wires that I assume is the 5-volt power supply from the ECM that the first fault references.

VIDA says one possible source for the low signal in the 5-volt power supply is a short-circuit to ground in the 5-volt supply cable. Another is a damaged sensor to the 5-volt supply cable. I swapped the boost-pressure sensor from an identical Volvo that is operating normally. Changing sensors didn't help, so I assume it's a short-circuit to ground in the 5-Volt supply cable.

How can I find and fix a ground in the 5-volt supply cable?

I would appreciate any tips and insight. Thank you!

Post by **jimmy57** » 05 Nov 2014, 11:05

You are looking for the violet/white wiare at MAF, FPS, A/C high side pressure sensor (on the receiver driver next to condenser below RH hood latch), boost and charge air temp sensor on intercooler exit, and the wiring for oil level sensor if it exists in the harness on engine.
You wwill need to measure the voltage on that wire at any place and then un plug all the items one at a time to eliminate the short being in one of the sensors. Next will be monitoring voltge and find any location where the harness to any of those items or the engine harness as it goes from ECM box on RH side to engine, has a place where it may be touching metal. Move the harness at any suspicious spot while watching the voltmeter. If the harness has the wiring for oil level sensor (used on the R models but I can't recall if the plug for it is in harnesses on the 2.5T's) then look for it under intake in about the center of engine to see if it is the problem.

casbah99 · Post by **casbah99** » 05 Nov 2014, 19:09

Thank you! Earlier tonight I was looking at the harness in question just to see if there was any visual damage to it where a wire may have been crimped, but the sun went down on me. I should have mentioned that I did have to replace the bumper and radiator after an accident.

I'll get out there tomorrow as soon as I can for a closer examination and then troubleshoot the areas you mentioned.

Thanks again, and I'll report back.

draser · Post by **draser** » 06 Nov 2014, 10:55

The other thing when you have a bunch of low signals like that is to check your charging system to make sure you have the 14.4v with engine running. For the sake of electrical engineering accuracy your 5v supply is not shorted out it's just either loaded down/overloaded or not getting enough juice from car's electrical system.

Post by **jimmy57** » 06 Nov 2014, 12:44

I discounted charging system affecting Vref as on this Volvo many other modules would report low voltage as well as a electrical system service message if the voltage was low enough to cause Vref to go down there would a host of other issues and almost assuredly a message about electrical system service needed in the DIM.
I viewed a wiring diagram for the car in question and the ECM has one wire out to the sensors he has codes for and for the others I listed to inspect. There is a direct relationship for his codes to a single circuit. Low power supply will cause codes not directly related to a single circuit.

casbah99 · Post by **casbah99** » 06 Nov 2014, 20:31

Thanks for the new information. The short daylight hours have kept me from getting some serious work on it done, but I'll report back as soon as I do.

I did find that the battery read 12V without the engine running. Unfortunately the car won't start now, so I can't test the battery with the car running. And that's despite the fact that I charged the battery yesterday. I'll try jumping it off tomorrow, and plugging it to VIDA to see what the latest faults are.

casbah99 · Post by **casbah99** » 07 Nov 2014, 15:44

Now it won't start. It tries, but it won't turn over and run. I swapped another battery from another S60 that I know is good, and it still wouldn't start.

Plus, I couldn't get DICE to read the car in VIDA, despite trying for hours. Does the car have to be running for DICE to recognize it? I've only gotten it to work once and can't recall what obscure magic I used to get that archaic software to work the one time.

I'm wondering if the alternator was just dying and is now fully dead.

draser · Post by **draser** » 09 Nov 2014, 08:04

I'd check batt cables for clean and firm connection, then put voltmeter across and crank. If volts go below 9.6 it's either batt or engine. Try taking plugs out, remove fuel pp fuse and crank to clean cylinders. See if you smell a lot of gas and plugs are wet.

casbah99 · Post by **casbah99** » 09 Nov 2014, 18:13

Thanks. I'll have someone test the battery while I try starting it tomorrow. And I'll take out the fuel pump fuse and the plugs and try starting it.

casbah99 · Post by **casbah99** » 29 Jan 2015, 08:24

Hi. Thanks for all of the suggestions. It turns out I did have a cut wire coming from the ECM to the modules that were registering the errors. Once I found and soldered it together the car ran perfectly again.

Thanks again.