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Old 02-17-2013, 03:13 PM
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Engine Coolant Temperature Sensor issue

I have an L67 S/C V6 in my Volvo wagon. Just putting it back together after paint and getting ready for spring. I started the engine yesterday, first time during reassembly, and the cooling fans did not come on. Got a little hotter then I was happy with so I shut it down. Today I checked all the components. Bench tested the fan relay, it lit a test light on the bench. Made sure I had power to the relay with key on. Checked continuity of the ECT fan circuit to the correct pins on the PCM, all good. ECT has a 5V reference with key on. I did not check continuity between ECT and the temp gauge since that gauge works. I also jumped 12V to the fans and they run strong.
Is it possible that the ECT will send a signal to the gauge but not to the PCM calling for fan on?

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Old 02-18-2013, 10:35 AM
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Anybody, LA Tech, help please!!
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Old 02-18-2013, 03:09 PM
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shop manual

Get the shop manual at ALLDATAdiy.com Leading Source of Factory Automotive Repair Information and then you can troubleshoot. Saves a lot of guesswork.
Does the engine get hot enough to run the fan in the winter?
Does the fan run with A/C on?
Possibly a different sensor is used for the fan.

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Old 02-18-2013, 03:45 PM
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Quote:
Originally Posted by evolvo View Post
I have an L67 S/C V6 in my Volvo wagon. Just putting it back together after paint and getting ready for spring. I started the engine yesterday, first time during reassembly, and the cooling fans did not come on. Got a little hotter then I was happy with so I shut it down. Today I checked all the components. Bench tested the fan relay, it lit a test light on the bench. Made sure I had power to the relay with key on. Checked continuity of the ECT fan circuit to the correct pins on the PCM, all good. ECT has a 5V reference with key on. I did not check continuity between ECT and the temp gauge since that gauge works. I also jumped 12V to the fans and they run strong.
Is it possible that the ECT will send a signal to the gauge but not to the PCM calling for fan on?
it would be easier to try to help if you gave the year and model of the Volvo. Also the engine size as L67 will not be a listed engine size. Have you checked with a scan tool to see what the ECT (engine coolant temp) is. Some vehicles use a different sensor for the computer and the gauge.

More info = more help
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Old 02-18-2013, 04:25 PM
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OK guys, the engine is from a '98 Pontiac Grand Prix GTP, that is, an L67 S/C V6! Look at my photos. I have a Helms factory manual that I used to double check all the PCM pin locations and wire routing. I drove the car for 3 years in primer then blew it apart for paint two years ago and I'm just now putting it back together. Cooling fans worked great for those 3 driving years. Like I stated before I have checked continuity on all wires, the relay works on the bench, relay has power with the key on and the ECT sensor has a 5V reference, also with the key on, or Hot In Run as stated in the Helms manual. The temp gauge on the instrument cluster works. Again, is it possible that the ECT sensor can send a signal to the temp gauge on the panel, but not send a signal to the PCM calling for fan on? Besides the possibility of the PCM having failed in this one function (horrible thought!!!) I'm hoping I can replace the ECT sensor in the block and everything will work OK. Any thoughts?
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Old 02-18-2013, 04:37 PM
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The coolant sensor on that should be a 3 pin...one for ground and one for gauge and one for PCM.
If you check live data, if you can...watch the coolant temp. The fans should kick about 230-235- F. They also should kick on with an AC input , but only when the AC pressure transducer signals a high enough head pressure...so watch the coolant temp.
If the temp gets pretty high, and the live data also shows a cooling fan request, check to be sure the signal to energize the relay is coming from the PCM to turn it on.
GM ecm s and PCM s are kinda noted for a malfunction in the driver for the cooling fans.
You can get a new sensor and plug it in, but dont install it. Then watching live data with the engine not running ( makes it easy) heat the sensor with a lighter, watching the temp on the scanner,to see when the PCM kicks the fan relay.Saves time and fuel and the motor doesnt have to run to warm up....boil over ....etc.
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Old 02-18-2013, 06:46 PM
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LATECH,
Thanx, good info. Yes it is a 3 pin ECT. Can I check live data with a tool like this? MS509 OBD2 OBDII Scanner Code Reader Live Data for GM Ford Toyota 96 Current | eBay. If so I can borrow one from the local parts store, although it would probably be a good tool to own! I'll assume that checking the new ECT with a lighter would be with KEY ON, yes?
I really wish you hadn't told me this, though. "GM ecm s and PCM s are kinda noted for a malfunction in the driver for the cooling fans." I have a lot of money into getting my PCM customized.
Speaking of A/C. A friend and I worked out a schematic to have the PCM run the Vintage Air heat/cool unit. I went to the Pick & Pull and got an A/C pressure sensor with a short section of tubing that has the schrader valve. Adapted this to the trinary port on the VA drier and wired it to the PCM. Looking forward to seeing if this is gonna work.
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File Type: pdf volvo AC.pdf (30.2 KB, 33 views)
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Old 02-19-2013, 09:51 AM
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That scanner says it WILL display live data, in the product description.
And yes, you need to have the key on for the test, also you need the key on for the PCM to transmit Live data.
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Old 02-19-2013, 10:02 AM
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Also...if you determine the PCM wont run the fans, you can use a stand alone fan controller such as a Derale unit.
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