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LS Swap Sensor Upgrade typography

A Properly Tuned Engine Requires Optimum Sensor Readings

BY Ryan Manson Photography by THE Author

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hen it comes to prepping a junkyard, pull-out LS engine for a new truck build, one of the first things we like to do is replace all the necessary OE sensors with the corresponding items from Duralast Parts. These engines, whether clean as a whistle or filthy as a feral cat, don’t tell their true story regarding what’s going on inside and the miles of torture and torment they may have endured. While the interior of the engine may not be easily inspected, the consumable components on the exterior are easily accessed while the engine is out of the vehicle, something that becomes more difficult after the engine’s installed. Tight, confined space due to firewall clearance can make accessing the cam position and oil pressure sensors a challenge in some trucks, while the low-mounted crank sensor can be hard to access due to various header designs and so on.

Built to meet or exceed OE specifications, Duralast’s LS sensors make for great peace of mind insurance before finalizing an engine swap and provide a bulletproof foundation to provide accurate information to the engine’s ECU, whether it’s an OE unit or, like our setup, an aftermarket EFI system from FiTech. While it may seem redundant to replace seemingly good sensors with new, we’ve found that oftentimes these sensors are damaged when the engine is pulled due to operator error and plain old carelessness. In fact, when we inspected our LS engine, we found an oil pressure sensor that was completely broken off. This is one of those sensors that can be hard to access once in the vehicle due to clearance between the intake and the firewall.

Typically, an LS swap is being made for peace of mind and reliability, so it seems natural to want to ensure that all the necessary components are new and in primo shape from the start. Like a house built on a solid foundation, new, properly functioning sensors from Duralast ensure we won’t be spinning our wheels and chasing our tails trying to track down the reason for a poorly running engine.

an assortment of sensors from Duralast sit atop a work surface
1. We ordered up an assortment of sensors from Duralast Parts to replace the old sensors on our junkyard LS engine.
close view of a damaged sensor located at the top of the LS engine block
2. We’ll start at the top of the block where the damaged sensor sits.. Damaged sensors from careless removal is not uncommon when it comes to “pull-out” LS engines.
mechanic loosens a nut to remove a sensor
3. On many LS engines and all iron-block designs, the cam position sensor sits at the top of the block next to the factory oil pressure sensor. We’ll install both sensors while we’re at it.
close view of the oil pressure sensor on the left (Duralast PN PS391) and the cam position sensor (PN SU1277DG) on the right installed on the block
4. Here are the two sensors installed in their place, the oil pressure sensor on the left (Duralast PN PS391) and the cam position sensor (PN SU1277DG) on the right.
close up of the valley cover with a new knock sensor
5. While we’re up top, two new knock sensors (PN SU1282) are installed in their respective location in the valley cover.
the oil pressure gauge is mounted in the lower mounting point using an adapter plate while the knock sensors are in their stock location
6. These three sensor locations moved over the years depending upon application, early versus late, so the differences are worth pointing out. Here, the oil pressure gauge is mounted in the lower mounting point using an adapter plate while the knock sensors are in their stock location for many of the later LS engines (LS3 for example).
front view of the LS block
7. The camshaft position sensor was also moved from the top of the block to the timing cover on many LS applications.
mechanic lays out and LS wiring harness
8. Laying out an LS wiring harness for the first time can be an intimidating affair for first timers and veterans alike. But with a little patience the harness can be organized so that the pigtails for each sensor are in their relative location and can be connected from there. Our FiTech EFI harness made mating the proper connectors with the correct sensors easy as the entire harness is clearly labeled.
close up of a connected sensor labeled knock
9. Additionally, every sensor features a unique connector design, making it impossible to connect the knock sensor connector to the crank position sensor.
close up of a connected sensor labeled CKP
10. Speaking of crank position sensors, there are two different designs that appear throughout the LS timeline, a 24x and 58x reluctor wheel design. These usually differentiate between a gray-colored sensor (the later 58x design) and a black (24x), but we’ve found 58x sensors in both colors. Most early LS engines and all iron block designs used the 24x setup. All LS engines use the same mounting location on the lower, passenger side just above the starter.
a set of Duralast ignition coils (PN C1208-8) and plug wires (PN 4713) installed to the block
11. The last handful of parts that our junkyard engine required was a set of Duralast ignition coils (PN C1208-8) and plug wires (PN 4713). We didn’t get the stock coil mounting plate with our engine and final coil location is yet to be determined, dependent upon final valve cover selection.
the idle air temperature (IAT) sensor
12. In addition to the basic set of OE sensors on our LS engine, there are another handful of sensors that are strictly related to the FiTech EFI system. These include the idle air temperature (IAT) sensor …
the throttle position sensor (TPS)
13. … throttle position sensor (TPS) …
the idle air control (IAC) motor
14. … idle air control (IAC) motor …
the 3-BAR manifold absolute pressure (MAP) sensor
15. … 3-BAR manifold absolute pressure (MAP) sensor …
the coolant temperature sensor (CTS)
16. … coolant temperature sensor (CTS) …
a pair of wideband oxygen (O2) sensors

17. … and a pair of wideband oxygen (O2) sensors.

In the Garage Tech Center box
Duralast Parts
(800) 288-6966
duralastparts.com
FiTech
(951) 340-2624
fitechefi.com