These instructions apply to the Lexus LS Mk1 (UCF10) 1988-1993.
For other models, please choose your vehicle here.
The original, first-generation Lexus LS 400 (XF10) — the car that launched the Lexus brand at the start of the 1990s — handles its keys very differently from any modern Lexus, so most online “how to change a Lexus key battery” guides simply do not apply. On this car the metal ignition key is a plain mechanical blade with no electronics inside it at all. The remote locking, where fitted, lives in a separate keyless-entry remote — a small keychain pod that rides alongside the key rather than folding out of it. Not every early LS 400 left the factory with one; keyless entry was a higher-trim and optional feature, so plenty of these cars only ever had the bare metal key. If your remote pod has stopped locking the doors from across the driveway, the coin cell inside it is the first and cheapest thing to change.
How to Tell the Fob Battery Is Dying
- Shrinking range. You have to stand right beside the car for the doors to respond, where the remote once worked from several metres away. On a car this age that gradual fade is the classic flat-cell symptom.
- The remote’s little indicator light dims or stops. If the pod has a status LED, it will flash weakly or not at all on a button press once the cell is low — a quick way to confirm it is the remote, not the car’s receiver, at fault.
- It works only sometimes, especially first thing on a cold morning. A near-flat coin cell struggles to deliver the brief burst of current the transmitter needs when it is cold.
- Nothing at all, yet the doors still lock perfectly with the metal blade in the door. That points squarely at the remote rather than the central-locking system.
A coin cell in a remote of this era typically lasts two to four years. Bear in mind these remotes are now over three decades old, so intermittent behaviour can also be a tired transmitter or corroded contacts — but always rule out the cheap flat battery first.
The Battery You Need
This is the one spec you must confirm from the cell itself rather than trust to a chart. The first-generation LS 400 was built across several years and its remote appeared in more than one version, and owners report different coin cells — a 3-volt lithium type in the CR1216 / CR1616 / CR2016 family is what turns up in these early pods. The only reliable answer is the code stamped on the cell you take out. So open the remote first, read the printed code — for example CR2016 — and buy that exact cell. They are all inexpensive lithium button cells sold in any supermarket; the difference between them is thickness, and the wrong thickness either will not seat or will not make contact. Choose a good branded cell, as cheap ones sag under load and give short range even when new.
Method — Opening the Separate Remote Pod
- Work over a light surface with a fine cross-head (Phillips) and a small flat-blade screwdriver to hand.
- Look for a retaining screw. Many of these pods have a single small screw on the back; undo it and the halves separate. If there is no screw, the case clips together — find the seam that runs around the edge.
- Split the case by easing the flat-blade tip into the seam and twisting gently. Take it slowly — three-decade-old plastic is brittle and the tabs crack easily.
- Note which way the old cell sits before you touch it — whether the marked ‘+’ face points up toward the cover or down into the holder — then lift it out.
- Fit the new cell the same way round, handling it by the edges so skin oils do not foul the contacts, and press it fully home under its clip.
- Close the case until the seam clicks flush, refit the screw if there was one (snug only, the housing is plastic), and test lock and unlock.
⚠️ Match the orientation of the cell you removed. A coin cell forced in the wrong way round will not power the transmitter and can discharge against the contacts, so copy the exact position of the old one rather than guessing.
Did It Work?
Stand back a few metres and press lock, then unlock. Full range should return at once and the doors should respond first time; any status LED should flash brightly again. Test with the car’s own 12 V battery healthy, since a weak car battery can make the central locking sluggish and muddy your result.
If a Fresh Cell Doesn’t Fix It
- Re-check the code and the seating. If you fitted a thinner cell than the holder expects it may not be touching both contacts — confirm you bought the exact code printed on the original.
- Clean the contacts. On a remote this old, light corrosion or finger grease on the metal terminals is a common cause of dropouts; wipe them with a dry cloth or a cotton bud.
- Suspect the remote itself. If a known-good, correct cell still gives nothing, the transmitter may simply have failed after thirty-odd years — not unusual on early keyless pods.
- Rule out the car. If the metal key also struggles to lock the doors, the fault is in the central-locking or the car’s 12 V supply, not the remote.
New Key or Spare — Why It’s a Dealer or Locksmith Job
Here the original LS 400 is refreshingly simple in one respect and awkward in another. The ignition key has no transponder chip — this car predates chip-in-key immobilisers — so a spare mechanical key is just a blade cut to the lock, with nothing to program. That part an auto-locksmith can do cheaply. The keyless remote is the harder half: the first-generation pods cannot be self-programmed the way later Lexus fobs can, the early-1990s cars use a different radio frequency from mid-decade models, and a replacement remote has to be matched and paired to the car’s receiver by a dealer or specialist. In short, changing the battery keeps your existing paired remote working; sourcing a brand-new one is the job that needs professional help.
Frequently Asked Questions
What battery does the original Lexus LS 400 remote take?
A small 3-volt lithium coin cell — owners report cells in the CR1216 / CR1616 / CR2016 family across the different first-generation pods. Because it varies, open the remote and buy the exact code printed on the cell you remove rather than relying on a generic chart.
Is the remote part of the key or separate?
Separate. On the first-generation LS 400 the metal ignition key and the keyless-entry remote are two different items, and the remote was fitted only to higher-trim or optioned cars — so some of these cars have no remote at all.
Do I have to reprogram the remote after changing the battery?
No. Swapping the cell leaves the remote’s existing pairing untouched, so it works immediately. Programming only comes into it when you fit a completely new remote, which on these early cars is a dealer or locksmith task.
Does the ignition key have a chip in it?
No. The first-generation LS 400 uses a plain mechanical key with no transponder, so a spare ignition key is simply cut to the lock — no electronic coding needed. Only the separate remote carries any electronics.
How long should the remote battery last?
Around two to four years from a fresh cell, though the age of the remote itself matters as much as the battery on a car this old.
Can I still get into and drive the car if the remote is dead?
Yes. The metal key locks, unlocks and starts the car entirely on its own — the remote only ever added convenience, so a flat coin cell can never strand you.
If the doors or locking started behaving oddly around the same time as an electrical niggle rather than a fading remote, the cause may sit deeper in the car’s wiring than the key. Checking for any stored fault code first can save a lot of guesswork — see what the codes mean at autodtcs.com.
Independent guide — not affiliated with Lexus. Always follow your official service manual and safety precautions. Read our full disclaimer.