High Voltage Junction Box Failure. Stop Safely Now. No Start.

[Daguerre]

Sharing this for those who may have a similar issue. Vehicle required a tow to dealer for repair 5,000 miles from home.

Details. Maverick Hybrid Lariat, 4K Tow Package, towing a 1500 lb ProLite trailer across the US.
Electric cooler plugged into the 120V bed receptacle. Occasional laptop recharging via console 120V outlet.
1) First hint of trouble in hindsight...Upon departure before hooking up the trailer, there was no power at either 120V inverter outlets. Power restored after a few minutes with the engine running. (I suspect now that the 12V battery system was in battery saver mode)
2) Second hint of trouble. About 2000 miles in, stopping for the night, and turning off the truck, the engine shuddered for a second, similar to the effect of "dieseling".
I tried a tank or two of higher octane fuel (91). I had been using 87.
3) Trouble. April 22. In Needles CA, stopping for the night, the engine "shuddered" again on shutdown. (Obviously not a gas issue). In hindsight, it was the electric clutch between the gas engine and electric motor not disengaging. THIS TIME the Hybrid System Fault instrument warning light came one along with the Hybrid System Fault instrument warning light Truck would not start or shift out of park. Tried calling Ford Roadside Assistance but it was after hours and not much help available at 8 pm. CA time (11 pm est Ford Canada time). Did some googling to find that the shuddering is due to the electric/gas clutch not disengaging. Also, found that I could reset the computer DTC with a sequence of flashing the highbeams five times followed by pressing the brake pedal three times. The truck started and we were able to drive to our campsite. We were able to complete our journey to Yosemite National Park and drive without the trailer connected for a week, and several days after while towing.
4) Trouble again. When stopping for dinner on May 7, the engine shuddered. Was able to restart right away and shuddered again on stopping. First time this happened. After dinner, the truck started. The next day we drove through mountains and stopped several times without issue.
5) Stranded. Friday, May 8, 5 pm. While stopping at Monarch Pass, CO, at the continental divide, the engine shuddered and the Hybrid System Fault instrument warning light, battery warning, and Stop Safely Now, message appeared. Trouble code reset did not work. I disconnected the 12V battery and waited 10 minutes. This also did not help.

At this point a huge thanks to Beaver Redfeather. He and a crew of workmen arrived on the scene. His friend Chad had a flatbed towtruck and within a half hour arrived to tow us 28 miles to Faricy Boys Ford in Salida CO. Chad was fantastic. The dealer was closed until Monday morning. When he unloaded the truck and trailer he went home to get his Snap ON scanner. He cleared the DTCs from the computer but the following three DTCs remained.

U3012-00 Control Module Improper Wake-up Performance-Current DTC- Warning Lamp On.
P0AA1-00 Hybrid/EV Battery Positive Contactor Circuit Stuck Closed - Current DTC.
P0563-00 System Voltage High-Current DTC- Warning Lamp On.

Luckily Chad was friends with Layo, Master Mechanic at Faricy Ford. A quick call to him confirmed that nothing could be done until the dealership opened on Monday morning. Note - On Sunday moring, on a hunch, I checked by Ford Pass app and saw that the car had gone into battery saver mode. I went to the Maverick and tried to start it. All systems were normal and the Ready light appeared. We decided it best to have Layo check it over the next day.

Diagnostic thought process between Layo and myself on Monday morning. It was great to be able to speak directly with mechanic as want to relay all the above information. All indications were that the 12V battery was low, causing a cascading effect of the above systems failure. I explained that we had been driving in tow-haul mode for about a week through the mountains. This keeps the system in gas mode only. We wondered that since there was no drain on the hybrid battery, but LOTS of regenerative charging going down steep mountain grades that the charging system cycled off to protect the battery from overcharging. With the charging system OFF, was it possible that the dc/dc converter no longer charged the 12V battery either?

Layo checked the 12V battery. State of charge was 33%. The 12V battery was recharged and tested. It passed the test. Further pinpoint testing lead to the High Voltage Battery Junction Box failure. The part was ordered on Monday, arrived Tuesday and we were back on the road Wednesday. All Warranty repairs. We're hoping to recover 1500 CDN for travel interruption for three nights hotel, meal as and 400 dollar towing.

Once again. Huge thanks to Beaver, Chad, Layo. AND Mark and Lynne. A nice couple who invited us to stay in their home for two days awaiting repairs. Couldn't have found a better place to break down so far from home.

We drove home the rest of the way in Nomal mode...Tow-Haul mode is unnecessary with a light trailer and 4K towing it seems. Wondering if using Tow Haul mode over taxed the relay in the HVJB causing it to be stuck closed, causing the shudder, and eventually failing.

21 MPG average for the entire trip. Not bad for towing a trailer.

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[Maverick123]

Looks like an awesome trip! Glad your issue got resolved (relatively) easily for the return home

 

[SafetyGuy]

Sharing this for those who may have a similar issue. Vehicle required a tow to dealer for repair 5,000 miles from home.

Details. Maverick Hybrid Lariat, 4K Tow Package, towing a 1500 lb ProLite trailer across the US.
Electric cooler plugged into the 120V bed receptacle. Occasional laptop recharging via console 120V outlet.
1) First hint of trouble in hindsight...Upon departure before hooking up the trailer, there was no power at either 120V inverter outlets. Power restored after a few minutes with the engine running. (I suspect now that the 12V battery system was in battery saver mode)
2) Second hint of trouble. About 2000 miles in, stopping for the night, and turning off the truck, the engine shuddered for a second, similar to the effect of "dieseling".
I tried a tank or two of higher octane fuel (91). I had been using 87.
3) Trouble. April 22. In Needles CA, stopping for the night, the engine "shuddered" again on shutdown. (Obviously not a gas issue). In hindsight, it was the electric clutch between the gas engine and electric motor not disengaging. THIS TIME the Hybrid System Fault instrument warning light came one along with the Hybrid System Fault instrument warning light Truck would not start or shift out of park. Tried calling Ford Roadside Assistance but it was after hours and not much help available at 8 pm. CA time (11 pm est Ford Canada time). Did some googling to find that the shuddering is due to the electric/gas clutch not disengaging. Also, found that I could reset the computer DTC with a sequence of flashing the highbeams five times followed by pressing the brake pedal three times. The truck started and we were able to drive to our campsite. We were able to complete our journey to Yosemite National Park and drive without the trailer connected for a week, and several days after while towing.
4) Trouble again. When stopping for dinner on May 7, the engine shuddered. Was able to restart right away and shuddered again on stopping. First time this happened. After dinner, the truck started. The next day we drove through mountains and stopped several times without issue.
5) Stranded. Friday, May 8, 5 pm. While stopping at Monarch Pass, CO, at the continental divide, the engine shuddered and the Hybrid System Fault instrument warning light, battery warning, and Stop Safely Now, message appeared. Trouble code reset did not work. I disconnected the 12V battery and waited 10 minutes. This also did not help.

At this point a huge thanks to Beaver Redfeather. He and a crew of workmen arrived on the scene. His friend Chad had a flatbed towtruck and within a half hour arrived to tow us 28 miles to Faricy Boys Ford in Salida CO. Chad was fantastic. The dealer was closed until Monday morning. When he unloaded the truck and trailer he went home to get his Snap ON scanner. He cleared the DTCs from the computer but the following three DTCs remained.

U3012-00 Control Module Improper Wake-up Performance-Current DTC- Warning Lamp On.
P0AA1-00 Hybrid/EV Battery Positive Contactor Circuit Stuck Closed - Current DTC.
P0563-00 System Voltage High-Current DTC- Warning Lamp On.

Luckily Chad was friends with Layo, Master Mechanic at Faricy Ford. A quick call to him confirmed that nothing could be done until the dealership opened on Monday morning. Note - On Sunday moring, on a hunch, I checked by Ford Pass app and saw that the car had gone into battery saver mode. I went to the Maverick and tried to start it. All systems were normal and the Ready light appeared. We decided it best to have Layo check it over the next day.

Diagnostic thought process between Layo and myself on Monday morning. It was great to be able to speak directly with mechanic as want to relay all the above information. All indications were that the 12V battery was low, causing a cascading effect of the above systems failure. I explained that we had been driving in tow-haul mode for about a week through the mountains. This keeps the system in gas mode only. We wondered that since there was no drain on the hybrid battery, but LOTS of regenerative charging going down steep mountain grades that the charging system cycled off to protect the battery from overcharging. With the charging system OFF, was it possible that the dc/dc converter no longer charged the 12V battery either?

Layo checked the 12V battery. State of charge was 33%. The 12V battery was recharged and tested. It passed the test. Further pinpoint testing lead to the High Voltage Battery Junction Box failure. The part was ordered on Monday, arrived Tuesday and we were back on the road Wednesday. All Warranty repairs. We're hoping to recover 1500 CDN for travel interruption for three nights hotel, meal as and 400 dollar towing.

Once again. Huge thanks to Beaver, Chad, Layo. AND Mark and Lynne. A nice couple who invited us to stay in their home for two days awaiting repairs. Couldn't have found a better place to break down so far from home.

We drove home the rest of the way in Nomal mode...Tow-Haul mode is unnecessary with a light trailer and 4K towing it seems. Wondering if using Tow Haul mode over taxed the relay in the HVJB causing it to be stuck closed, causing the shudder, and eventually failing.

21 MPG average for the entire trip. Not bad for towing a trailer.

Thank you for your detailed explanation of your trip and the issues you had!

I am glad you were able to get it sorted out, once you had it towed to the dealer.

I am sure others will read your story and also heed the warning signs you experienced, and your thoughts on not draining the HVB at all on a road trip where you are towing.

Have a good one,

Andy

 

[Finnster]

Wondering if using Tow Haul mode over taxed the relay in the HVJB causing it to be stuck closed, causing the shudder, and eventually failing.

That is a great question!
Perhaps some one here who knows when Tow Haul Mode should actually be used can answer it!
I just made my first towing run this evening 12 miles, essentially all downhill (slightly) towing a 2,000 pound trailer and garden tractor.
I used Tow Haul Mode, and I thought: This is stupid! From now on I'll likely use Normal Mode, unless the trip is definitely uphill!

 

[tiktokbrainrot]

The 12v charging system is separate from the HV charging system. If the HV battery is full, the 12v charging system should be charging the lead acid. It only turns off when you hit 30% on the HV battery. And since you have a trailer connected, it SHOULD be trying to keep the 12v at 100% SoC. Given the lead acid was at 33%, even though it passed the test I'd be looking at replacing it anyway, it shouldn't be going that low during normal operation. (especially if you are regening with a full HV battery, if Ford was clever that setup should result in a massive charge for the 12v battery...).

The junction box is a remarkably simple piece of hardware physically. It's mostly solid state electronics, with the contacts being the only moving part and supposedly sealed. It sounds like yours was a ticking time bomb from the factory and while the long trip may have finally caused it to fail, I wouldnt be worried about tow/haul mode. If that was enough to melt the contacts we'd be seeing this a lot, I dont think anyone here has reported this kind of failure before.

 

[HeyBales]

Tow/Haul isn't going to cause more regen then would be accomplished with the brake pedal, or the ICE running more to get up inclines.

What it does do is prioritizes have the HVB closer to the 70% SOC side rather than allowing the 30% side.

That way when extra power is needed - you got enough juice from the HVB to throw the Traction Motor into the mix. Similar in Sport mode.

In Normal / Eco mode it's willing to keep using that HVB for extra TM power down in the 50% SOC range - not because needed, just to keep away from 70%.

But going down an incline with a load - likely to be onto the brake unless your selected Drive mode does regen automatically at higher level and brakes not needed for the incline.
But brake in regen, or coast with high regen - both result in the same amount going to HVB, or if not available, wasted spinning the ICE with no fuel for air braking.
Watch your instant fuel mileage - should be 999.9.

But as soon as you go into the pads - you are getting the max regen rate possible - no matter the drive mode. (not the max amount of regen, just the rate).

 

[allc0re]

Glad you made it home safely and the repair work was under warranty. Hopefully you get reimbursed too.

Thanks for the detailed explanation of what happened and what fixed it. That will likely help others.

 

[Dad]

What a journey! Sorry for the trouble you had, but look at the unintended consequences. If ever anyone needed a revelation of the goodness in people, you certainly found it and by sharing it with the club it will ripple out to many others. I experienced much the same when the brakes went out on my RV in mid-Los Angeles. Made an emergency stop in the closest side street I could find . . . blue collar neighborhood. People were wonderful while I waited 12 hours for a tow. Asked if I was hungry or if I needed anything. One guy got out of his warm bed at 1:00 am to move his car so the tow truck would have a unobstructed approach. My faith in the overall goodness of people was renewed.
Glad your issue got resolved with the least amount of inconvenience.

 

[rk06382]

What year is your "Maverick Hybrid Lariat with 4K Tow Package?"

Sharing this for those who may have a similar issue. Vehicle required a tow to dealer for repair 5,000 miles from home.

Details. Maverick Hybrid Lariat, 4K Tow Package, towing a 1500 lb ProLite trailer across the US.
Electric cooler plugged into the 120V bed receptacle. Occasional laptop recharging via console 120V outlet.
1) First hint of trouble in hindsight...Upon departure before hooking up the trailer, there was no power at either 120V inverter outlets. Power restored after a few minutes with the engine running. (I suspect now that the 12V battery system was in battery saver mode)
2) Second hint of trouble. About 2000 miles in, stopping for the night, and turning off the truck, the engine shuddered for a second, similar to the effect of "dieseling".
I tried a tank or two of higher octane fuel (91). I had been using 87.
3) Trouble. April 22. In Needles CA, stopping for the night, the engine "shuddered" again on shutdown. (Obviously not a gas issue). In hindsight, it was the electric clutch between the gas engine and electric motor not disengaging. THIS TIME the Hybrid System Fault instrument warning light came one along with the Hybrid System Fault instrument warning light Truck would not start or shift out of park. Tried calling Ford Roadside Assistance but it was after hours and not much help available at 8 pm. CA time (11 pm est Ford Canada time). Did some googling to find that the shuddering is due to the electric/gas clutch not disengaging. Also, found that I could reset the computer DTC with a sequence of flashing the highbeams five times followed by pressing the brake pedal three times. The truck started and we were able to drive to our campsite. We were able to complete our journey to Yosemite National Park and drive without the trailer connected for a week, and several days after while towing.
4) Trouble again. When stopping for dinner on May 7, the engine shuddered. Was able to restart right away and shuddered again on stopping. First time this happened. After dinner, the truck started. The next day we drove through mountains and stopped several times without issue.
5) Stranded. Friday, May 8, 5 pm. While stopping at Monarch Pass, CO, at the continental divide, the engine shuddered and the Hybrid System Fault instrument warning light, battery warning, and Stop Safely Now, message appeared. Trouble code reset did not work. I disconnected the 12V battery and waited 10 minutes. This also did not help.

At this point a huge thanks to Beaver Redfeather. He and a crew of workmen arrived on the scene. His friend Chad had a flatbed towtruck and within a half hour arrived to tow us 28 miles to Faricy Boys Ford in Salida CO. Chad was fantastic. The dealer was closed until Monday morning. When he unloaded the truck and trailer he went home to get his Snap ON scanner. He cleared the DTCs from the computer but the following three DTCs remained.

U3012-00 Control Module Improper Wake-up Performance-Current DTC- Warning Lamp On.
P0AA1-00 Hybrid/EV Battery Positive Contactor Circuit Stuck Closed - Current DTC.
P0563-00 System Voltage High-Current DTC- Warning Lamp On.

Luckily Chad was friends with Layo, Master Mechanic at Faricy Ford. A quick call to him confirmed that nothing could be done until the dealership opened on Monday morning. Note - On Sunday moring, on a hunch, I checked by Ford Pass app and saw that the car had gone into battery saver mode. I went to the Maverick and tried to start it. All systems were normal and the Ready light appeared. We decided it best to have Layo check it over the next day.

Diagnostic thought process between Layo and myself on Monday morning. It was great to be able to speak directly with mechanic as want to relay all the above information. All indications were that the 12V battery was low, causing a cascading effect of the above systems failure. I explained that we had been driving in tow-haul mode for about a week through the mountains. This keeps the system in gas mode only. We wondered that since there was no drain on the hybrid battery, but LOTS of regenerative charging going down steep mountain grades that the charging system cycled off to protect the battery from overcharging. With the charging system OFF, was it possible that the dc/dc converter no longer charged the 12V battery either?

Layo checked the 12V battery. State of charge was 33%. The 12V battery was recharged and tested. It passed the test. Further pinpoint testing lead to the High Voltage Battery Junction Box failure. The part was ordered on Monday, arrived Tuesday and we were back on the road Wednesday. All Warranty repairs. We're hoping to recover 1500 CDN for travel interruption for three nights hotel, meal as and 400 dollar towing.

Once again. Huge thanks to Beaver, Chad, Layo. AND Mark and Lynne. A nice couple who invited us to stay in their home for two days awaiting repairs. Couldn't have found a better place to break down so far from home.

We drove home the rest of the way in Nomal mode...Tow-Haul mode is unnecessary with a light trailer and 4K towing it seems. Wondering if using Tow Haul mode over taxed the relay in the HVJB causing it to be stuck closed, causing the shudder, and eventually failing.

21 MPG average for the entire trip. Not bad for towing a trailer.

 

[Daguerre]

What year is your "Maverick Hybrid Lariat with 4K Tow Package?"

2025. Also AWD, I forgot to mention.

 

[rk06382]

2025. Also AWD, I forgot to mention.

Your profile says 2022 Maverick.

 

[Daguerre]

I traded it in for a 2025 AWD 4K Lariat Hybrid. These features were not available in 22 when I joined the group. I neglected to upgrade my vehicle profile.

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