If I clear my Leaf's DTCs with LeafSpy Pro, can a service mechanic recover them?

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Well-known member
Dec 11, 2018
Oahu, Hawaii.
I have a technical question about LeafSpy Pro.

If I used LeafSpy Pro to delete the DTCs created by a fault in a cell of the main battery... which caused the red triangle... can those DTCs still be recovered by a Nissan service center’s mechanic?

The rest of the story:
We’re shopping for a new-to-us used Leaf. Today we drove to another town to test-drive one of the candidates. That test drive went well, and we’ll discuss it in another post.

As we were going up a steep highway to meet the owner for the test drive, we almost didn’t get there. On the steepest part of the uphill route, the weak battery on our 2017 Leaf shut us down. This is our Leaf that we've already filed a claim on for a replacement battery:

Other than losing bars, we've never had any trouble until today. The car was apparently using full power to go 60 MPH uphill, and at least one cell of the battery couldn’t handle the discharge load. I’m guessing that one of the 192 cells dropped voltage faster than the rest of the pack, and that divergence must have been considered a fatal error by the battery management software.

I suspect it’s one of the cells that’s causing the warranty claim on the car. The battery’s continued losing capacity for the last 11 months and it’s now down to 7 out of 12 bars. However this was our first incident.

The dashboard lit up like a yellow & red Christmas tree, the car shifted to neutral, and an alert flashed that power had been shut off. (I caught a quick glimpse of the alert, but then I was busy dodging traffic to get to the shoulder.) All we could do was coast to the side of the highway. Considering the steep hill, it was a short coast.

Once we were stopped, I cycled through the display but couldn’t find the screen alert. The car had shifted to Neutral, and I could put it in Park, but it wouldn’t go to Drive or Reverse. The red triangle fault let me shut off the car and turn it back on, but even after several tries it would not let me shift from Neutral to Drive. I was sure we’d have to call for a tow truck. Game Over.

Then I remembered: we were going for a test drive, so I’d brought my OBD-II dongle with my iPad and its copy of LeafSpy Pro.

We plugged the OBD-II into our dashboard, brought up the app on the iPad, and read the diagnostic trouble codes. There were several DTCs (with short descriptions) for a battery failure caused by a cell voltage. I tried shutting off the car and restarting it, then re-reading the codes, but they didn’t clear.

Then I remembered that LeafSpy Pro can clear the DTCs.

I’ve never cleared DTCs before. It took me a couple of attempts, and I had to dive into at least two specialty menus with warnings like “DO NOT CLEAR these codes if you do not understand them.” After about three rounds of clearing DTCs and restarting the car, it agreed to go into Drive. We got up the rest of the hill and over to the other town.

I’m pretty sure that when the car first shut down and coasted, its weak cell was unloaded. Free from the heavy drain of driving uphill, it started to recover its voltage. Once the overall voltages got back into spec (and once we finally cleared the DTCs) we could drive the car again.

We did the test drive of the other car (that went fine), and returned home without incident.

Once we were home I re-ran the car’s DTCs, but none of them even rise to the level of a yellow triangle, let alone the red triangle.

This 2017 Leaf has already been validated for the battery warranty and we have a J code case number. Our local Nissan service center doesn’t need to see us anymore, and we don’t see a reason to share this incident with them.

We plan to sell this 2017 Leaf into Nissan’s battery-warranty buyback program.
At some point perhaps it’ll be inspected. If a mechanic plugged in an OBD-II reader and read the codes, would they find any record of the DTCs that I deleted?
The warnings in LEAF Spy Pro about being sure you want to clear the DTC's are there because the codes are gone once cleared. Therefore, you do not need to worry about the cleared DTC's getting into the wrong hands.
GerryAZ said:
The warnings in LEAF Spy Pro about being sure you want to clear the DTC's are there because the codes are gone once cleared. Therefore, you do not need to worry about the cleared DTC's getting into the wrong hands.
Excellent. Thank you for the reassurance!
DTCs, or Diagnostic Trouble Codes, are codes generated by a vehicle's onboard diagnostics system when it detects a potential issue. LeafSpy Pro is a third-party app used with Nissan Leaf electric vehicles to access detailed information about the car's systems, including DTCs.

If you clear DTCs using LeafSpy Pro, it means you are essentially erasing the recorded fault codes from the vehicle's memory. However, the ability of a service mechanic to recover these cleared DTCs depends on a few factors:

Type of DTCs: Some DTCs are stored in non-volatile memory, meaning they persist even if the vehicle is turned off. Others are stored in volatile memory, which is erased when the vehicle is turned off. If the DTCs you cleared are stored in non-volatile memory, a mechanic may still be able to retrieve them.

Mechanic's Tools: Professional mechanics often use more advanced diagnostic tools that can access a vehicle's memory and history. These tools may be able to retrieve cleared DTCs, especially if they are stored in non-volatile memory.

Time Elapsed: If some time has passed since you cleared the there might be a reduced chance of recovery. Over time, the vehicle's memory may overwrite or discard older DTCs.

It's important to note that clearing DTCs without addressing the underlying issue may make it more challenging for a mechanic to diagnose and fix problems during a service visit. Additionally, tampering with a vehicle's diagnostic information could have implications for warranty claims or other service-related matters.

If you're planning to visit a service mechanic and you've cleared DTCs using LeafSpy Pro, it's advisable to inform the mechanic about this action. Open communication can help them understand the context and provide better assistance with your vehicle's diagnostics and repairs.
I use professional quality scan tools on other vehicles and LEAF Spy Pro with the LEAF (because other tools will not work). Personally, I would never tell a dealer that I cleared DTC's unless I had to clear them just to get the car to move so I could get it to the dealer. DTC's will reappear if there are legitimate error condition(s) rather than just module, power supply, or loose connection glitches.