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RandyA

Volvo D12 Boost Sensor Replace Short Cut

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If you have ever visited the OTR Performance web site and watched the video on replacing the turbo boost/temperature sensor you are aware of their statements that if you have over 300K on your engine you should replace the sensor as both mileage and performance are downgraded by the old sensor. They sell the sensor for $150 but are currently out of stock.

 

I decided to replace my sensor. I found a new OEM sensor on-line for $85.00.

 

The replacement requires removing several pieces on the left of the engine to access the socket for the plug on the end of the wiring harness (watch video). I decided NOT to pull the parts off and rather splice the exterior wiring from the old harness to the new harness. I learned to solder and splice in the womb and have been doing it successfully for all my life. For this project I staggered the splices on the four wires, made a Western Union splice, soldered the connection and covered with heat shrink tubing. The secret to a good splice is proper soldering. Make sure you have enough heat to produce a shinny silver joint when the solder cools. A dull gray color indicates a "cold solder joint" that will introduce resistance and fail.

 

The photos below show how I replaced my sensor externally by making splices in the four wires. BTW - have yet to make a trip to see if there is a difference or improvement but looking at the old sensor I feel like something good will come of the project.

 

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Accessible OEM boost sensor next to valve cover.

 

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New and old sensors. Note the condition of the old sensor (pretty ugly and covered with carbon not to mention a deformed tip!)

 

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Sensor mounting hole

 

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Four wires spliced

 

 

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Wire loom back in place covering the spliced/soldered/heat shrink joints.

 

TIP:

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TIP:

You will have your butt on top of the power steering unit during most of the job. It gets uncomfortable very quickly.

 

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TIP:

Put a couple of small shop rags on top of the canister, invert a small pail over the canister and shop towels then put a large towel on top of the pail. Your butt will thank you!

 

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Job finished - maybe 30 to 40 minutes total.

 

TIP:

When using electrical tape in the engine compartment use a good quality tape like 3M #33. Cheap off-brand tapes are prone to having the adhesive melt and the tape comes loose. Also put a zip tie around the open end of your tape when you finish wrapping to prevent the end from lifting.

 

I'll post the final on-the-road results next week.

Edited by RandyA

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Only thing I'd be concerned with is that if this is a normal .5V - 4.5V sensor, your splice may have changed the impedance giving offset data to the ECM. Perhaps someone with a bit more of an electronics backround will confirm or dispel that theory.

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Stekay - Randy is a Retired EE professor. I doubt that it would change the impedance and Randy would be the one to ask. (Just saying - a lot of hidden talent on the forum) .

 

Besides the tape (good advice, we only used the cheap for wire pulling and such, never for the install, 88 is also good, 8.5 mils vs 33's 7 mil thickness)

 

3M 33+ tape - http://solutions.3m.com/wps/portal/3M/en_US/EMDCI/Home/Products/ProductCatalog/?N=5432987+3294355633&rt=rud

3M 88 Super - http://solutions.3m.com/wps/portal/3M/en_US/EMDCI/Home/Products/ProductCatalog/?N=5432987+3294355634&rt=rud

 

Another good tip (in addition to the soldering) put the heat shrink on first. I know - duh - but I've done it many, many times and the end result is always the same (kicking myself around the yard). And as a former certified HV splicer, back in the wiped lead and cambric days, such things are not pretty.

 

on edit - Randy--keep us posted on the difference - if noticeable. Thanx

Edited by Bill B

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Stekay - Randy is a Retired EE professor.

 

LOL, I'll make a note of that. ALWAYS good to have a competent electrical guy around. And judging from his input and videos, I think along with Jack Mayer, we've got a systems guy as well.

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Only thing I'd be concerned with is that if this is a normal .5V - 4.5V sensor, your splice may have changed the impedance giving offset data to the ECM. Perhaps someone with a bit more of an electronics backround will confirm or dispel that theory.

You are right to question altering a sensor cable. But, since inductance and capacitance are not critical factors in altering the DC signal quality on this particular cable, impedance is not a factor to be concerned with. I would not advise doing this with a shielded cable. Now, if a splice were made with wire nuts or butt connectors or an attempt to solder the wires resulted in a cold solder joint one could critically alter the signal value. Eventual corrosion in the spliced joint will result in unwanted resistance that will change the value of the signals. It is best to make a strong mechanical joint like the Western Union Splice and then solder. Often "quick splices" with butt connectors work OK initially but rapidly deteriorate - especially in hot and wet environments. I have encountered insulation literally burned off of wires with currents as low as 5 amps as a result of heat generated by the resistance introduced with butt connectors. It is a snowball effect as a small resistance introduces just enough heat to cause dissimilar contraction/expansion of the two metals which results in more resistance from oxidation/corrosion deposits and then it is all downhill - even on low level current lines like this sensor.

 

BTW - self fusing silicone tape is a good fall back when one forgets to put the heat shrink tubing on before finalizing a spliced connection. A mistake often made with heat shrink tubing is to use a match or lighter to heat the tubing. Such a method results in inconsistent shrink and often burning. A heat gun is a better choice.

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Randy, I've been splicing like that for years (where it matters), and I never knew the name for the splice. Thanks. I learn something every day !! :)

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Another good 'topcoat' is Scotchkote - http://solutions.3m.com/wps/portal/3M/en_US/EMDCI/Home/Products/ProductCatalog/~/3M-Scotchkote-Electrical-Coating-FD-in-brush-top-15-oz-can?N=5584029+3294648449&rt=rud - Use paper to 'protect' from drips. Put this over the top of your tape wraps. It remains flex for a long time - personal experience, I can back to a splice I did in a galvanizing plant (hot corrosive atm) in the middle 70's, fast forward to 2007 still in place and pliable.

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I design wiring harnesses for Agricultural use, and we often "parallel splices" http://www.waytekwire.com/item/33070/Molex-19205-0004-8GA-Brazed-Parallel-Connector/ I won't use a "butt splice". A butt splice creates 2 joints, current must flow from the wire across the joint, thru the splice, across the 2nd joint, to the other wire. A parallel connector crushes the wire strands directly together. Current flows directly from one wire to the other. No, its not as good as a solder joint, but close. If you then solder the splice, it can be the best of both worlds.

However, soldering does have a couple downsides. If not properly sealed, a solder joint can actually "encourage" corrosion. I'm no chemist...but I've seen solder joints with corrosion forming around the wires at the solder. For my business, the worse problem is flexibility. A solder joint creates a hard "break point" where the solder meets the wires. In conditions on vibration and wire motion, we find that unsoldered parallel splices outperform soldered joints, because wires too often break right beside the solder. Double layers of sealant coated heatshrink can help this problem.

 

If you must use a butt splice, use the heatshrink type.

 

Of course, the larger wiring companies often use a compression ?ultrasound? welding process on the splices--its pretty cool to see and very durable. But I don't think any of us have the need to buy a multi $$$ machine to wire up the Jackalopee!

 

When I was in Africa installing a generator system, we had no electricity and no heat gun. All the splices had to be heatshrunk with a lighter. Talk about a LOUSY pain....!

 

Always enjoy hearing about your projects Randy, and usually learn more than a few tips while reading! Keep em coming!

Edited by Jeff- C IL

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Phil - It was an ebay listing. Just looked and it is no longer there. Found several for Volvo price of $149 - not a good deal.

 

Jeff - taking lead out of solder has helped to abate the corrosion issue we had a few years back. I still have some lead/tin mix electrical solder but prefer not to use it. Thanks for adding details about your work.

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Randy, where did you get the sensor??

Phil - I checked the invoice and it came from Filter Barn. I tried their web site but couldn't find the sensor <_< . Don't know if they have more or not....... they do show a phone number (608) 592-7584

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I have replaced my boost sensor which I also purchased from OTR, I also spliced the new wire harness into the old harness rather than going all the way and plugging the new sensor plug where it should have plugged in the first place, I used electrical connectors with shrink tube around them and wonder if this did not defeat the purpose of installing a new boost sensor................?

Would like someones opinion on this one as an increase in performance of the engine was not really noted..?

 

Thanks.

 

Rene.

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I have replaced my boost sensor which I also purchased from OTR, I also spliced the new wire harness into the old harness rather than going all the way and plugging the new sensor plug where it should have plugged in the first place, I used electrical connectors with shrink tube around them and wonder if this did not defeat the purpose of installing a new boost sensor................?

Would like someones opinion on this one as an increase in performance of the engine was not really noted..?

 

Thanks.

 

Rene.

It should not defeat the purpose right now. But, over time moisture will get inside the shrink connectors and small pockets of corrosion will occur around the mechanical connection and dissimilar metals between the crimp connector and copper wire. (I cannot define how long "time" is). As they develop, resistance will increase and possibly alter the voltage (signal) through/from the sensor. You see, there are two parts to the sensor. One component alters its design resistance based on pressure, the other component alters its design resistance based on temperature. The voltage returned to the EECM as a result of internal changes in the sensors is interpreted by the EECM as one of numerous other signals that ultimately impact performance. If any one of the sensors that feed signals to the EECM degrades (like in a "bad" connection) but does not simply quit working the EECM will not send the optimum performance info to the injectors. This is why I said solid contact between spliced wires properly soldered would provide the best chance at not eventually corroding. There are even better ways than solder but they are not readily available to the average HDT do-it-yourself guy. Signal degradation can also occur across any mechanical connection which includes the OEM male/female interfaces or plugs.

 

OK - that was a long BS explanation of what can happen with connections - any connections. Just file it away in a need-to-know file and check connections if something goes sour that alters or eliminates sensor info to the EECM. This is true for any data/signal line - not just our trucks.

 

As noted, whether you see an improvement in performance will depend of the condition of the old sensor. In my case, my old sensor was not sending good signals to the EECM - thus I had an improvement. Without measuring sensor output with instruments we are not likely to own or want to pay for, sensor changing is actually a crap shot. Fortunately the boost/temperature sensor is inexpensive and easy to change compared to some of the others. If you did not see a performance change don't feel bad - your routine sensor preventative maintenance is good insurance against future problems. You also know you have not been wasting money on fuel that was not optimally being used by your engine. I was throwing away 2 to 4 cents in fuel for every mile I drove. Over 40,000 miles that adds up to $800+ bucks. B)

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This is my old one after I used carburetor cleaner to blow out the soot. Under the soot and around the thermistor was a jelly like substance. Not sure if it was always that way or if it was a mild epoxy that instantly turned to jelly when it came in contact with the cleaner. The splitting of the metal around the thermistor is the way it looked when I removed it.

 

Picture

 

I guess you can't share pictures from Google since the link will not show the picture name/extension.

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TFS - that picture sure showed how bad yours was. Let us know how strong your mileage improvement is.

Edited by HERO Maker

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HD, that would be my question as well, it is the gauge in the dash that isn't working. I'd like to check the sensor first, before replacing it.

 

PS, not on topic but the Moody Blues are going to be in Florida in March for those old enuf to remember them. Melbourne is 1 location.

 

Getting my ticket today.

Edited by Roger Dickinson

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Do the cluster self test (might be called gauge test, truck not at home to check today) and see if the gauge works first . The little stepper motors are a common fail.

 

Nigel

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By memory key on, up arrow to diagnostics enter, cluster self test enter, gauge test enter. All gauges should sweep to max then min then half then min. You will see if any don't work or don't travel all the way. I had a mobile guy come and fix 3 motors in mine and it was a couple of hundred dollars.

 

Nigel

Edited by Nigel

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this is what the sensor should read voltage wise but you'd need to removed the sensor and kludge a way to apply the "test" pressures while the sensor is powered up (engine not running).

 

Manifold Pressure Voltage
0 kPa (0 psi) 1.18 v
50 kPa (7 psi) 1.73 v
100 kPa (14.5 psi) 2.29 v
150 kPa (22 psi) 2.84 v
200 kPa (29 psi) 3.40 v

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