U0100 on Jeep: How to Diagnose & Fix
Lost Communication with ECM/PCM
3 Jeep models · 3 documented issues · 3 critical · $200-$1,800 repair
U0100 on Jeep by model: symptoms, diagnosis and fix
Owner reports and NHTSA complaints describe repeated dead 12V batteries and no-start conditions on Grand Wagoneer, often after sitting overnight or a few days. The pattern is consistent with parasitic draw from modules not going to sleep (commonly telematics/infotainment-related controllers), leading to low voltage and cascading network faults.
Common Symptoms
- No-crank/no-start after sitting
- Multiple warning lights after jump start
- Remote start inoperative
- Battery voltage low message
- Repeated need for jump starts or battery replacement
How to Fix
Perform a parasitic draw test with an ammeter and use a scan tool to identify modules staying awake; update software per applicable Stellantis service bulletins and replace the failing module if it will not sleep. Replace the 12V battery if it has been deeply discharged multiple times and verify charging system output.
What you need to diagnose it
The fix here starts with a test, not a part — which repair you need depends on what the test finds.This issue involves U codes, which a basic engine-code reader cannot see.At least one code uses a manufacturer-specific format. No scanner recommendation is shown because family-level coverage cannot prove it can read that code.
UNI-T UT210E Low-Current DC Clamp Meter
1 mA resolution on the 2 A range — a 0.1 A meter reads a 50 mA drain as zero
$40–$70View
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Testing and isolating the fault is DIY work. Replacing or reprogramming a control module is not — most are VIN-programmed, so a new one does nothing until a shop codes it to your car. Check for an open recall or service bulletin before buying anything.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Duralast Platinum H7-AGM Group 94R main batteryOEMDuralast H7-AGM / SKU 319458
Confirm installed group, CCA, vent, terminal layout and VIN bec
- Duralast Platinum H8-AGM Group 49 main batteryOEMDuralast H8-AGM / SKU 319459
Do not substitute it for an installed H7 without confirming tray/
- Duralast Platinum AUX14 Group 400 AGM auxiliary batteryOEMDuralast AUX14 / SKU 755654
It is not the main battery; verify VIN/equipment and the installed auxiliary battery label
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Wrangler 4xe owners report repeated dead 12V auxiliary batteries and, in some cases, complete electrical shutdowns. Several owners found the included Level 1 charger drains the 12V battery after the high-voltage pack reaches 100%, leaving the vehicle unresponsive within days. Beyond no-starts, some 4xe vehicles abruptly lose power or shut off while driving (often when EV range is exhausted), and owners have had to disconnect and reconnect the 12V battery to revive the vehicle, sometimes with persistent warning lights afterward. Dealers frequently cannot locate the parasitic drain even when the 12V battery tests good.
Common Symptoms
- Dead 12V battery / no-start
- Complete electrical shutdown
- Vehicle loses power or stalls while driving
- Battery drains after reaching full charge
- Requires disconnecting/reconnecting 12V to restart
- Persistent warning lights after restart
How to Fix
Apply all available 4xe software/PCU updates (some shutdown reports trace to OTA update regressions, and updates have also addressed charging-state drain). Test the 12V auxiliary battery and charging system; replace a weak 12V battery and verify proper terminal connections. As an interim measure many owners unplug the Level 1 charger once the pack reaches 100% to stop the drain. For drive-cycle shutdowns/loss of propulsion, have the dealer pull stored faults and check for related recalls/customer-satisfaction campaigns, as some 4xe loss-of-power conditions overlap with open safety actions.
Sources for this issue (2)
On early Patriots a manufacturing adhesive problem inside the powertrain control module allowed the circuit board to crack, cutting engine control and causing a stall. Chrysler recalled the affected 2009 Jeep Patriot, Jeep Compass and Dodge Caliber vehicles under NHTSA campaign 08V528000 in October 2008. This is a distinct failure from the crank sensor stall and from TIPM faults, and it is limited to the recalled build population - it is not a general 2007-2017 PCM defect.
Common Symptoms
- Engine stalls while driving
- No start
- Multiple unrelated powertrain codes at once
- Loss of communication with the PCM on a scan tool
How to Fix
Run the VIN at nhtsa.gov/recalls; if it falls in 08V528000 the dealer replaces the PCM at no cost with no mileage or age limit. A replacement PCM outside the recall must be programmed to the VIN and to the SKIM immobilizer, so it is a dealer or capable-shop job costing roughly $600-$1,100.
Sources for this issue (1)
U0100 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does U0100 mean on a Jeep?
U0100 stands for "Lost Communication with ECM/PCM." U0100 is a network communication code meaning a module has lost communication with the engine control module / powertrain control module (ECM/PCM) over the vehicle's data bus. The ECM/PCM is the brain that runs the engine, so when other modules can no longer 'talk' to it, the effects can be serious — a no-start, stalling, multiple warning lights, and many other modules logging faults at once. This is almost always a wiring, connector, power/ground, or bus fault, or a failure of the ECM/PCM itself, rather than a single sensor. It should be diagnosed promptly because the vehicle may be undrivable. On Jeep it is documented across 3 models: Grand Wagoneer, Wrangler, Patriot.
What are the most common causes of U0100?
The most common causes of U0100 are: Loss of power or ground to the ECM/PCM, CAN bus wiring damage, short, or open circuit, Corroded, loose, or damaged connectors at the module, Blown fuse feeding the ECM/PCM, Failed ECM/PCM, Another faulty module pulling down the data bus, Water intrusion or corrosion in a connector/harness. The specific cause varies by vehicle.
How much does it cost to fix U0100 on a Jeep?
Published repair estimates on Jeep range from $200 to $1,800 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for U0100 on a different make?
View U0100 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.