Short to ground on a sensor 5 volt reference wire or in the harness, often from chafed insulation; A faulty sensor fed by the auxiliary 5 volt supply pulling the voltage down internally; Corroded, damaged or loose connectors at sensors or at the engine control module; Poor or missing ground or low battery or system voltage affecting the module's supply; Water ingress or damage to the harness near the engine bay or bulkhead; Internal fault in the engine control module's 5 volt regulator.

P1488

Auxiliary 5 Volt Supply Output Too Low.

Jeep
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
4: AreaAuxiliary emission controls
88: FaultThe specific fault in that area

What it means

P1488 on a Jeep means the engine control module has detected that its auxiliary 5 volt reference supply is too low. This supply feeds certain sensors, and the module monitors its voltage. If it falls below the expected range for longer than the allowed time, the code is set and the fault lamp may come on.

Symptoms

Malfunction indicator lamp on
Poor or uneven running, hesitation or flat spots
Rough idle or occasional stalling
Reduced power or the engine entering a limp-home strategy
Other sensor fault codes stored at the same time
Difficulty starting in some cases

Possible causes

Short to ground on a sensor 5 volt reference wire or in the harness, often from chafed insulationlikely
A faulty sensor fed by the auxiliary 5 volt supply pulling the voltage down internallylikely
Corroded, damaged or loose connectors at sensors or at the engine control modulepossible
Poor or missing ground or low battery or system voltage affecting the module's supplypossible
Water ingress or damage to the harness near the engine bay or bulkheadpossible
Internal fault in the engine control module's 5 volt regulatorrare

How to diagnose

Read all stored codes and freeze frame data, and note any other sensor circuit codes that share the same 5 volt supply
Check battery condition and charging voltage, and inspect the main grounds and power feeds
Visually inspect the engine harness and connectors for chafing, rubbing, corrosion, water or previous repairs
Using the wiring diagram for the specific model and engine, identify which sensors share the auxiliary 5 volt supply
Unplug the sensors on that supply one at a time while monitoring the reference voltage, to see which one restores it
Measure the 5 volt reference at the module and at each sensor connector, and test the wiring for shorts to ground and resistance
Check the module's power and ground supplies before suspecting the module itself
Clear the code and road test to confirm it does not return

How to fix

Repair or replace the harness section that is shorted or chafed, and secure it away from rubbing points
Replace the sensor found to be loading the 5 volt supply
Clean or replace corroded or damaged connectors and terminals
Restore poor grounds or power feeds and correct any charging or battery fault
Replace or repair the engine control module only after wiring and sensors are proven good, and have it programmed as required

Can I keep driving?

Medium severity

The car can usually be driven short distances, but fix it soon as the affected sensors may give wrong readings and cause poor running or stalling. Avoid long journeys if it hesitates, stalls or goes into limp mode.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.