I was driving home recently with the family from Texas Roadhouse when the LEAF made a beeping noise and I noticed warning lamps on the dash. One warning lamp was the EV System Warning Lamp. In addition to the warning lamps I also noticed that the distance to empty gauge was showing dashes. Dashes in place of miles normally occurs when the traction battery has a very low charge. However the car was 2/3rds full and it continued to show 2/3rds full after the dashes appeared.

EV System Warning light and loss of estimated range after glitch. Click to enlarge

The car drove normally. After we got home I restarted the car and everything was normal. Over the next day or two I did notice that the LEAF was more pessimistic about the range remaining compared to its normal over optimistic estimates. The estimates returned to normal within 36 hours. It seemed like a computer in the car responsible for estimating range rebooted itself and reset settings while being driven.

Not knowing what could cause such a glitch I did take it by the dealer for diagnosis. The car did register a fault code the dealer was able to read which indicated erratic CAN voltage. The dealer could not reproduce the fault and cleared the error code.

3G telematics to blame?

Ever since Nissan replaced 2G telematics units with 3G telematics units many customers have complained of random CAN errors. In some cases this has been traced back to low 12v battery voltage causing an array of random and erroneous error codes.

Everything back to normal, except the low distance to empty estimate. Click to enlarge

The consensus in the LEAF community is that the 3G telematics unit consumes more power and the 12v battery has more of a challenge keeping up with demands from the cars electrical systems. I did use the cars remote A/C pre conditioning both prior to heading to the restaurant and prior to heading home. It’s quite likely that multiple requests back to back may have weakened the 12v battery. The 12v battery is just over 1 year old so I doubt it has gone bad. If I get more errors like this, I’ll opt for a larger capacity 12v battery that will not run low so easily.

The good news is that the car did not breakdown or lose power at any time. It seems the error was spurious. The LEAF after 123,000 miles has yet to leave me stranded at the side of the road. It has been a very reliable car, all other cars I’ve owned previously have broken down at least once. EV’s are remarkably reliable vehicles.