Battery / System Voltage Above Upper Limit
The CAT-SKIDSTEER-168-3 (CAT Skid Steer) diesel fault code means: Battery / System Voltage Above Upper Limit. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- DIY battery and wiring inspection: $0-$50 in supplies. Alternator replacement DIY: $150-$350 in parts. Professional diagnosis and alternator replacement at a dealer or shop: $300-$700 including labor. Battery replacement if overcharged and damaged: $100-$200 additional.
Down with a CAT fault on the road?
Get connected with a verified mobile diesel mechanic near you. Verified diesel & reefer techs, launching on the freight corridor.
Find a mobile mechanic →A $30 car code reader can't do diesel. The HD7000 reads full-system codes and does parked DPF regen, idle/speed-limit, and service resets from the cab — on everything from a 6.7 Cummins/Power Stroke/Duramax pickup to Class-8 trucks (Detroit, Paccar, CAT, Volvo, Mack, International).
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Full-system 6/9/16-pin diesel scan tool for Cummins, Paccar, CAT, Detroit and more — plug-and-play, no subscription. A cheaper way to read heavy-duty codes a basic OBD2 scanner skips entirely.
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Common Symptoms
- Cab display shows active fault code 168-3 with a yellow or red indicator lamp
- Battery or charging voltage reads above 16 volts on the dash gauge or CAT ET
- Machine may start and run but warning stays active throughout operation
- Electrical accessories such as cab lights or radio behave erratically or seem unusually bright
- In severe cases the battery swells, leaks, or smells like rotten eggs from overcharging
- Machine ECM may log repeated or intermittent 168-3 events in the fault history
- Alternator or battery gets noticeably hot to the touch after a short run time
Probable Causes (Ranked by Likelihood)
- Failed alternator voltage regulator allowing uncontrolled high charging output Very Likely
- External battery charger left connected and set too high while machine is also running Very Likely
- Faulty or corroded battery voltage sense wire giving the ECM a false high reading Likely
- Poor ground connection causing a floating reference voltage at the ECM battery sense circuit Likely
- Shorted or damaged wiring between alternator B+ output and ECM sense pin Possible
- Weak or sulfated battery that cannot absorb charge, allowing voltage to spike under load removal Possible
- Wrong alternator installed with a higher output voltage than spec for this platform Less Likely
Step-by-Step Diagnostic Procedure
Start with a key-off safety check. Disconnect any external battery charger before proceeding. A charger left on while the engine runs is the single fastest cause of this code.
With the engine running at high idle (approximately 2800 RPM), measure battery voltage directly at the battery terminals with a multimeter. Normal charging range is 13.8 to 14.8 volts DC. A reading above 15.5 volts DC confirms a real overvoltage condition, not a sensor fault.
If voltage is normal at the battery but the code is still active, suspect a wiring or sensor fault. Locate the ECM battery sense circuit in the machine harness (typically a dedicated sense wire separate from the main B+ feed). Check for chafing, corrosion at the connector, or a short to a higher voltage source.
Inspect the alternator output terminal and B+ cable for heat damage, melted insulation, or loose connections. A loose connection can spike voltage momentarily and trigger 168-3 even if steady-state voltage looks fine.
Check all battery ground straps and chassis ground points. Clean any corroded ground connections at the battery negative terminal, the chassis stud, and the engine block ground. A bad ground raises apparent voltage on the sense circuit.
Load-test the battery using a carbon pile or battery tester. A battery that will not hold a load can cause voltage spikes during load shedding (for example, when you release the lift arms). Replace a battery that fails a load test below 9.6 volts DC under load.
If charging voltage is confirmed high (above 15.5 volts DC) and the battery and wiring check out, the alternator voltage regulator is the prime suspect. On C2.2 and C3.3B machines the regulator is internal to the alternator. You will need to replace the alternator assembly or have it bench-tested at an electrical shop. This step requires a qualified technician if you are not comfortable with alternator work.
Connect CAT ET via the J1939 service port to review the exact voltage value the ECM is seeing in real time and to confirm the fault is active versus stored. CAT ET will also show you if the ECM itself is logging a sensor rationality failure versus a true electrical overvoltage event.
Frequently Asked Questions
What does CAT code 168-3 mean on a skid steer?
It means the ECM measured the battery or system voltage above its programmed upper limit, typically around 16 volts DC. The most common reasons are a failing alternator regulator that is pumping out too much voltage, or an external battery charger that was left connected while the engine was running. It is an SPN 168 FMI 3 fault on the J1939 network.
Can I still operate the skid steer with code 168-3 active?
You can usually move and work, but you should not ignore it. Sustained high voltage damages the ECM, sensors, solenoids, and the battery itself. If your battery is getting hot or swelling, shut the machine down immediately. Treat this as a same-day fix, not something to run through a whole rental shift.
How much does it cost to fix code 168-3?
If the fix is just disconnecting a misconnected battery charger or cleaning a corroded ground strap, it costs almost nothing. A new alternator runs $150 to $350 in parts if you install it yourself, or $300 to $700 at a shop with labor. If the battery was overcharged and damaged, add another $100 to $200 for a replacement battery.
Will this code come back after I clear it?
It will come back if the root cause is not fixed. If the alternator regulator is failing, it will keep overcharging and the fault will return within minutes of starting the machine. Clear the code with CAT ET or by cycling the key, then watch the voltage in real time. If it climbs above 15.5 volts DC again quickly, you have a genuine charging system problem that needs to be repaired before putting the machine back in service.