Problems with Molly

This is a blog post about the things that have not quite gone right with our Molly. We are just getting started here, but wanted to keep track of issues along the way.

1st ENG SYS alarm

Saturday, May 26, 2018. California/Arizona Border ~3,659 miles

It was hot, above 40ºC, and I was stuck in a long line of traffic waiting for inspection at the State of California Food & Agriculture Dept: Inspection Station, when Molly decided to light up with the first engine alarm. It was amber, meaning, get to FUSO when you can.

I pulled over at the first opportunity and rang FUSO. They wanted to tow me, but that was not really an option, as I had no way to get back to San Francisco after the truck would have been dropped somewhere. So, Fuso agent and I, jointly decided to stop the engine to see if it would reset and restart. I was worried it would not start again. But it did, and no alarm, so off I went.

At the time I did not know how to read the error codes. So not sure what the reported issue was.

2nd ENG SYS alarm

Wednesday, July 4, 2018. San Jose, 4,179 miles.

Planned to take Molly out for the 4th of July vacation day. But plans changed quickly after a Red ENG SYS alarm was displayed. The error code was SPN=3701 and FMI=-2, which is a bit meaningless to me. According to the manual this means “The value measured by component ‘Differential pressure sensor of diesel particular filter’ is too high.”. Also a little meaningless.

One of the possible failure modes is “Filter regeneration was not successful or not possible.”. This makes sense, as Molly was stuck in highway traffic while trying to do a DPF regeneraiton. Molly entered half power mode.

A visit to the local FUSO service center did not help. They found a different alarm, being “The coolant temperature is implausible”, which is an amber alarm. I guess this is related to the 1st ENG SYS alarm, and might not have reset. The FUSO service center removed the thermostat, everything looked ok, reset the code, did a regen, upgraded the software and a drive test. Not highly conclusive. Maybe the software upgrade would help, at least for the regen issue.

3rd ENG SYS alarm

Monday, September 3, 2018. Near Tahoe on Highway 80. 5,850 miles.

Returning from Tahoe, and caught in heavy highway traffic, we experiences our 3rd ENG SYS alarm, amber this time. The error code was SPN=520644 and FMI=31, the implausible coolant issue again. The thing is, the coolant was not high. Turning the engine off and on cleared the issue. I am starting to suspect that this issue occurs after fast highway speeds followed by stop and go traffic. Will see if this happens again.

20,000 miles later, this has never happened again.

1st Check Engine Light

Sunday, December 12, 2021. Near Seattle on Interstate 5. 24,217 miles.

Driving up to Deception Cove for the day, Molly’s Engine Light came on. The error code was SPN=520650 and FMI=0, which translates to “The emission value of the NOx sensor (raw value) is too high”. Could be a number of things, so will keep an eye on it and see if it self heals.

Well a few days later it did indeed self-heal, who would have guessed!. Did not even need to manually reset the MIL, as it cleared itself.

4th ENG SYS alarm – Serious this time

Friday, January 28, 2022. South East of Seattle. 25,411 miles.

It was Friday evening and about 10 minutes before getting to our camp site, Molly displayed an orange ENG SYS alarm. There was also a yellow DEF icon and the check engine lamp (MIL). The error code was SPN=520651 and FMI=0, which translates to “The learned values for component ‘NOx sensor 2’ are outside the permissible range. ( Lambda value )”. This particular error is only meant to turn on the engine check light, so something more complicated is going on. Could be a number of things, so will keep an eye on it and see if it self heals.

On Sunday morning I turrned on the ignition and the Eng Sys was still present, so decided to remove and clean the DEF dosing pump. Hoping that this might be the problem. We left the camp-site with the solid amber alert still present, waiting to see if it would disappear. Almost exactly 30 miles later the amber alert light turned into a red alert flashing alternatively with yellow accompanied by a loud buzzing sound. We pulled over to investigate. We knew this might happen when we left the campground.. After calling Fuso for some roadside assistance, which did not help as our coverage had expired, we decided to drive to the nearest Seattle area Fuso Service Center. Luckily it was only 8.4 miles away. We found a local hotel for the night. We where only 15 miles from home, but staying near the Fuso Service Center was the right thing to do, so we could get the repair going bright and early the next day.

The following morning we sweet talked Bobby (Service Manager) into taking Molly in and looking into the problem for us. They currently have a 2 month backlog, but they squeezed us in. Five days later, Molly was returned all fixed. Issue corrected by replacing two sensors; Exhaust Muffler NOx Sensor (MK668275) and Exhaust Oxygen Sensor (ME555789). All covered under the 5 year exhaust warranty.