An LS swap is the most popular engine conversion for VB–VK Commodores, HQ–WB Holdens and Toranas. Once the motor is in, one of the first questions is how to get proper gauges working. The original Holden gauges can't read LS senders, and the LS engine computer still needs its own factory sensors to run properly.
The answer is to run aftermarket senders alongside the factory sensors, not instead of them.
The problem: one hole, two sensors
Gen III and IV LS engines (5.7, 6.0 and 6.2 litre) have a factory oil pressure sensor and coolant temperature sensors wired to the ECU. If you remove the factory oil pressure sensor to fit a gauge sender, the ECU loses that input and the factory oil pressure reading goes with it.
Oil pressure: use an adaptor
The SAAS LS oil pressure adaptor screws into the factory M16 × 1.5 oil pressure port and gives you extra 1/8 NPT ports. You refit the OEM sensor into the adaptor and add a 1/8 NPT aftermarket sender in the spare port. The ECU keeps its reading and your gauge gets its own.
For engines with a 1/8 NPT oil port, a brass T-piece adaptor does the same job.
Oil pressure tips
- Use thread sealant sparingly. Many senders earth through their thread, and too much tape can stop them reading.
- Keep heavy senders supported. Long adaptor stacks can crack under vibration, so mount them where they're braced.
- Check pressure with a mechanical test gauge if the reading looks wrong. It rules out the sender before you blame the engine.
Water temperature: use an inline radiator hose adaptor
Finding a spare coolant port on a swapped LS can be awkward, especially with aftermarket water pumps or intakes. An inline adaptor that sits in the top radiator hose is the simplest fix:
Both accept a 1/8 NPT sender and include a grub screw for earthing. Fit the adaptor in the top hose, close to the engine outlet, for the most representative reading. Measure your hose's inside diameter before ordering.
Speedo signal
Most LS swaps also bring a gearbox change, and the original Holden speedo cable won't connect. You can drive an electronic speedo with either a GPS speed sensor or a converter that reads the gearbox's signal. See GPS speed sensor vs ESA-01 to work out which suits your car.
Putting the gauges in the dash
If you want the gauges to look factory in a VB–VK Commodore, our RetroTech dash kits put SAAS gauges in the original cluster position with no cutting. For HQ–WB Holdens, see our GTS dash and warning light guide.
FAQ
Can I use the LS factory sensor to drive my gauge?
Generally no. Aftermarket analogue gauges are calibrated to their own senders, and sharing a factory sensor can upset the ECU's reading. Run a separate sender.
Which gauges do I need for an LS swap?
At a minimum: speedo, tacho, water temperature, oil pressure, fuel and volts. Our SAAS accessories for LS and Commodore builds cover the senders and adaptors.
Will my fuel gauge work with the original tank sender?
Often not straight away. See why a new fuel gauge reads wrong and how to fix it without changing the sender.
Not sure what your build needs? Send us your engine, gearbox and car and we'll put together a parts list.