P0A0A: High-voltage interlock circuit fault: the hybrid system has lost its safety loop
High voltage system interlock circuit
Severity: Inspect soon
The interlock loop tells the computer that high-voltage connectors and covers are closed. When it reads open, the hybrid system can shut down, and Ford, Jeep and Chrysler bulletins list stalls, no-start or a Service Hybrid System message with this code.
It gets more serious if:
- Stop: Stop in a safe place and arrange a tow if a red triangle with a "Stop Safely Now" message appears, the car loses power, or it will not restart. Ford lists those messages with this code.
P0A0A in short
P0A0A means the computer sees the high-voltage interlock loop as open. That loop confirms the high-voltage connectors and covers are secure. Common causes are chafed or broken interlock wiring and poorly sealed or seated connectors. A stall, no-start or "stop safely" message is possible. High-voltage work is for a trained technician.
Hybrids and plug-in hybrids run a low-voltage signal loop through the high-voltage connectors and covers. If a plug is unseated, a cover is off, or a wire in the loop breaks, the loop opens. The computer treats that as unsafe to keep the high voltage live and can shut the system down, then sets P0A0A.
The bulletins in the cache point to two kinds of fault: wiring in the loop that has chafed, shorted to ground or broken open (Ford Fusion Hybrid, MKZ Hybrid and C-MAX), and high-voltage connectors that are not sealing or seating properly (Jeep Wrangler 4xe). Chrysler has also issued battery pack control module software updates for the Pacifica Plug-in Hybrid that mention this code.
The orange high-voltage cables and connectors can cause fatal shock. Nothing on this page asks you to open them. The safe steps are to read the codes, ask a dealer about open bulletins for your VIN and let a technician trained in high-voltage systems find the open point.
Most likely causes
Cause 1: Chafed, shorted or open wire in the interlock loop
Supported by vehicle data- Why it ranks here
- Ford has two bulletin families for this: one replaces intermittently open interlock wire sections on 2010-2011 Fusion and MKZ Hybrids, and one covers chafed interlock wiring near the traction battery on 2013-2016 C-MAX plug-ins.
- What would change this
- Rises if the fault comes and goes with engine or body movement, or with a Ford hybrid showing a "stop safely now" message. Falls if the connectors are found damaged or wet instead.
Cause 2: High-voltage connector not seating or sealing (water intrusion)
Supported by vehicle data- Why it ranks here
- Jeep lists P0A0A-00 on 2021 Wrangler 4xe with a Service Hybrid System message, and a separate bulletin has the orange seals on the P1 and P2 high-voltage connectors inspected for water intrusion.
- What would change this
- Rises if the code returns after a connector was reseated or the vehicle was washed, driven through water or left in rain. Falls if the seals and terminals are found intact.
Cause 3: Battery pack control module software (Pacifica Plug-in Hybrid)
Supported by vehicle data- Why it ranks here
- Chrysler issued four battery pack control module software bulletins (2023-2026 Pacifica Plug-in Hybrid) whose record text mentions this code; only the summary was read, so what the update changes for this code is not known.
- What would change this
- Rises if a dealer finds an open update for your VIN. Falls if the software is already current.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read all stored codes and note the dashboard message. Write down any "stop safely" or "Service Hybrid System" wording and any codes stored with P0A0A.
IfA Ford hybrid or plug-in shows a stop-safely message with U3012 or P0B37
It meansFord ties these to chafed or open interlock wiring.
Points to: Chafed, shorted or open wire in the interlock loop
IfA Jeep 4xe shows Service Hybrid System, or a Pacifica Plug-in Hybrid has the check engine light on
It meansCheck for open bulletins for the VIN.
IfNo pattern fits
It meansGo to a technician for the interlock inspection.
Step 2: Ask a dealer whether your VIN has an open bulletin, software update or recall for P0A0A.
IfA battery pack control module update applies and is not installed
It meansThe update comes first.
Points to: Battery pack control module software (Pacifica Plug-in Hybrid)
IfA connector seal bulletin applies to your Jeep
It meansA technician inspects the connector seals.
Points to: High-voltage connector not seating or sealing (water intrusion)
IfNothing applies
It meansA technician inspects the interlock loop.
Step 3: Have a technician trained in high-voltage systems check the interlock circuit and connector seals with the high-voltage system safely disabled.
Warning:High-voltage cables (orange) and connectors can cause fatal shock and must not be opened or tested by untrained people.
IfA chafed, shorted or open interlock wire is found
It meansThe wiring is repaired or replaced.
Points to: Chafed, shorted or open wire in the interlock loop
IfA damaged seal or a connector that is not seated is found
It meansThe seal, harness or component is replaced as the maker directs.
Points to: High-voltage connector not seating or sealing (water intrusion)
Symptoms
- Check engine light or a Service Hybrid System message
- Red triangle with a "Stop Safely Now" message (Ford hybrids)
- No start, or an intermittent no-crank
- Vehicle stalls or loses power while driving Gets more serious: stop and have it checked.
Compare with: Check engine light with loss of power
How to fix
This is a safety-critical system, so we explain the code but don't give repair steps. Have it inspected by a qualified technician.
On your vehicle
FordYour car
2010–2011 · Fusion
Supported by vehicle dataFord bulletin TSB-12-5-14 covers P0A0A with a red triangle and stop-safely message on the Fusion Hybrid; a trade article says the fix is an overlay harness for the interlock wires. Bulletin status is not verified.
2013–2016 · C-Max
Supported by vehicle dataTwo Ford bulletins list P0A0A with U3012 and P0B37 on the C-MAX plug-in hybrid, and one points to chafed interlock wiring near the traction battery. Status not verified.
TSB-12-5-14Status unverified
P0A0A with red triangle, stop-safely message or no start
2010–2011fusion · NHTSA 10044899
Ford hybrid interlock circuit bulletin; the NHTSA summary does not give the repair. A trade article says it installs an overlay harness kit to replace intermittently open interlock wire sections.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
SSM 46108Status unverified
C-MAX PHEV intermittent stall with U3012, P0B37 and/or P0A0A
2013–2016c-max · NHTSA 10090514
Inspect the low-voltage interlock circuits for chafing on the harness near the traction battery cover, repair the chafed wire and secure the harness.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
TSB 17-0015Status unverified
C-MAX Energi intermittent stall with U3012, P0B37 and/or P0A0A
2013–2016c-max · NHTSA 10095616
Follow the service procedure; the NHTSA summary does not say what the repair is.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
LincolnYour car
2011 · MKZ
Supported by vehicle dataThe same Ford/Lincoln bulletin covers the MKZ Hybrid. Status not verified.
TSB-12-5-14 (MKZ)Status unverified
P0A0A with red triangle, stop-safely message or no start
2011mkz · NHTSA 10044899
Same Ford/Lincoln bulletin as the Fusion entry, filed under the MKZ Hybrid.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
JeepYour car
2021–2026 · Wrangler
Supported by vehicle dataJeep lists P0A0A-00 with a Service Hybrid System message on the Wrangler 4xe, and a second bulletin has the high-voltage connector seals inspected for water intrusion. Status not verified.
2022–2026 · Grand Cherokee
Supported by vehicle dataRevision B of Jeep bulletin S2108000121 extends the P0A0A-00 Service Hybrid System entry to the Grand Cherokee 4xe. Status not verified.
S2108000121Status unverified
Check engine light and Service Hybrid System with P0A0A-00
2021wrangler · NHTSA 10198377
Service information for a 2021 Wrangler 4xe that sets P0A0A-00 (high voltage system interlock circuit "A" active). The summary does not give the repair.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
S2108000121 REV.BStatus unverified
Check engine light and Service Hybrid System with P0A0A-00
2021–2026wrangler, grand-cherokee · NHTSA 11028892
Revision B of the Jeep bulletin, extended to the Wrangler 4xe 2021-2026 and Grand Cherokee 4xe 2022-2026. The summary does not give the repair.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
08-131-21Status unverified
Possible water intrusion at the P1 and P2 high-voltage connectors
2021wrangler · NHTSA 10218554
Inspect the orange seals on the P1 and P2 connectors and replace them if needed, for a 2021 Wrangler 4xe with no start; P0A0A is among the codes found.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
ChryslerYour car
2023–2026 · Pacifica
Supported by vehicle dataFour Chrysler bulletins for the Pacifica Plug-in Hybrid update the battery pack control module for customers with the check engine light on; their record text mentions P0A0A. Status not verified.
08-126-26Status unverified
Battery pack control module updates (Pacifica Plug-in Hybrid)
2023pacifica · NHTSA 11030216
Software update for the battery pack control module; the NHTSA record text mentions P0A0A. What it changes is not in the summary.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
08-127-26Status unverified
Battery pack control module updates (Pacifica Plug-in Hybrid)
2024pacifica · NHTSA 11030217
Same as 08-126-26 for model year 2024.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
08-124-26Status unverified
Battery pack control module updates (Pacifica Plug-in Hybrid)
2025pacifica · NHTSA 11030214
Same as 08-126-26 for model year 2025.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
08-125-26Status unverified
Battery pack control module updates (Pacifica Plug-in Hybrid)
2026pacifica · NHTSA 11030215
Same as 08-126-26 for model year 2026.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Related codes
P0A0A questions
Can I fix P0A0A myself?
No. The interlock loop runs through high-voltage connectors and covers, and opening them risks fatal shock. A technician trained in high-voltage systems should inspect it.
Is it safe to drive with P0A0A?
Not reliably. The hybrid system can shut down without warning, and Ford lists stall and no-start with this code. Get it checked before relying on the car.
Sources and review
- Ford/Lincoln TSB 12-5-14 (NHTSA 10044899)
- Jeep S2108000121 (NHTSA 10198377, Rev. B 11028892)
- Hybrid high jinks (TSB roundup)
- Ford SSM 46108 (NHTSA 10090514)
- Ford TSB 17-0015 (NHTSA 10095616)
- Jeep 08-131-21 (NHTSA 10218554)
- Chrysler 08-124-26 to 08-127-26 (NHTSA 11030214 to 11030217)
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error