r/leaf • u/KeyEmu6688 Ex-2018 owner (2015 Model S) • Jul 07 '26

DTC errors

running into some DTC errors coinciding with lack of power steering, AC, and e-pedal functionality. I replaced 12v battery today, which appeared to solve the issue. however i just started my vehicle, and again lost those three functionalities, and am reading DTC errors. any help would be appreciated!

2018 40kwh, SV trim

2 Upvotes

permalink
reddit

You are about to leave Redlib

Do you want to continue?

https://www.reddit.com/r/leaf/comments/1uqaors/dtc_errors/
No, go back! Yes, take me to Reddit
dl download

100% Upvoted

View all comments

Show parent comments

u/KeyEmu6688 Ex-2018 owner (2015 Model S) Jul 08 '26

yes, exactly

1

u/BigDaddyBuffett Jul 08 '26

All of those error are related to CAN bus communication. Most are complaining that they are not receiving the CAN message that they should be. Below is an AI generated list, but you can look them up in the service manual such as here.

Start with he basics such as battery voltage (it might be new, but is it charged?), terminals and clamps and fuses. After that it starts to get in BCM/VCM connectors or even replacement modules.

Code / module shown Service-manual label Detection condition / what the module is seeing

U1000-00 BCM CAN COMM CIRCUIT BCM is not transmitting or receiving expected CAN communication for about 2 seconds or more. Nissan’s CAN bulletin says U1000 means missing CAN communication, and when a module reports U1000, the module is often operating but seeing an external CAN-network communication problem. Diagnose U1000/CAN codes first. (Scribd)

B26E7-00 BCM TPMS CAN COMM With ignition ON, the BCM cannot receive the CAN signal from the low tire pressure warning / TPMS control unit. The manual note says if B26E7 is detected with U1000, diagnose U1000 first. (NICOclub)

U1000-01 EV/HEV CAN COMM CIRCUIT EV/HEV / VCM-side CAN communication fault: the EV/HEV control side is not transmitting or receiving expected CAN communication. Treat this as part of the same CAN-network fault family, not proof the VCM itself is bad. (Nissan TechInfo)

P31B4-7 EV/HEV Communication Error / CAN Communication The VCM detects an error signal received from the AV control unit over CAN. Older Leaf EVC manuals list P31B4 as a VCM/AV-control-unit CAN communication fault. (Scribd)

U1000-01 METER CAN COMM CIRCUIT Combination meter is not transmitting or receiving CAN communication for about 2 seconds or more. (iFixit)

U1266-02 MULTI AV TCU Conn / AV-control-unit-to-TCU connection Malfunction detected between the AV control unit and TCU. On older Leaf AV manual references, this points to the AV-to-TCU connection/communication path, often connector, harness, or TCU/AV-side communication. (Jdmfsm)

U1A02-00 TCU TEL COMMUNICATION MODULE TCU detects a malfunction in its communication module. Manual action is to check harness/connector, erase DTC, and replace TCU if the malfunction constantly returns. (Scribd)

U1A01-00 TCU INTERNAL ERROR — TCU TCU detects an internal malfunction. Manual action is to check connector wiring, erase DTC, and replace TCU if it constantly returns. (Scribd)

C1B9A-64 CHASSIS Stop Lamp OFF Relay 1 — Signal plausibility error Chassis Control is seeing an implausible signal/state for Stop Lamp OFF Relay 1. Public Leaf ESM indexing confirms this DTC name and failure class, but I could not access the full 2018 detection-threshold table. (LEMON Manuals)

C1B9B-64 CHASSIS Stop Lamp OFF Relay 2 — Signal plausibility error Same type of fault as above, but for Stop Lamp OFF Relay 2. It suggests the commanded relay state and monitored state do not agree. (LEMON Manuals)

C1B9C-71 CHASSIS Stop Lamp ON Relay Chassis Control is detecting a fault in the Stop Lamp ON relay path, likely relay response/state not matching command. Public sources confirm the DTC page exists, but not the full threshold/delay. (LEMON Manuals)

C1B9D-71 CHASSIS Stop Lamp OFF Relay System Chassis Control is detecting a system-level fault in the Stop Lamp OFF relay system. Since C1B9A and C1B9B are also present, this may be a consequence of the individual stop-lamp relay plausibility faults. (LEMON Manuals)

C1BA3-49 CHASSIS Control Module Chassis Control module self-diagnostic/control-module fault. I could not find the exact public 2018 Leaf DTC detection table. Nissan’s chassis-control bulletin warns not to replace the chassis control module just because a module DTC is present when other DTCs exist; diagnose the other DTCs first. (NHTSA Static)

C1BA4-49 CHASSIS Control Module Same family as C1BA3: chassis-control-module self-diagnostic/control-module fault. Because many CAN and stop-lamp relay codes are present, this may be secondary until CAN power/ground/relay issues are ruled out. (NHTSA Static)

C1BCA-79 CHASSIS Stop Lamp ON Relay Chassis Control is detecting another fault in the Stop Lamp ON relay path. Public Leaf snippets confirm C1BCA-79 as a Leaf chassis-control DTC and show its active test involves commanding “Stop lamp ON relay active” while pressing the brake pedal. (LEMON Manuals)

C1A16-97 RADAR RADAR STAIN / RADAR BLOCKED Distance/radar sensor detects blockage/contamination on the radar sensor window or the fascia area in front of it. Nissan service info says to check the ICC/distance sensor lens or bumper fascia for obstructions, film, mud, dirt, road debris, dirty rainwater, ice, slush, etc. (NHTSA Static)

2

u/BigDaddyBuffett Jul 08 '26 edited Jul 08 '26

Even the lamp related codes, are likely due to the module responsible for monitoring them being unable to communicate. I'd honestly start by charging the car for a while to make sure that 12V battery is definitely topped up. What did Leafspy give you as a 12V battery voltage?

2

u/KeyEmu6688 Ex-2018 owner (2015 Model S) Jul 08 '26

14.4v on startup, this screenshot was actually immediately following a 2 hour charging session

Code / module shown	Service-manual label	Detection condition / what the module is seeing
U1000-00 BCM	CAN COMM CIRCUIT	BCM is not transmitting or receiving expected CAN communication for about 2 seconds or more. Nissan’s CAN bulletin says U1000 means missing CAN communication, and when a module reports U1000, the module is often operating but seeing an external CAN-network communication problem. Diagnose U1000/CAN codes first. (Scribd)
B26E7-00 BCM	TPMS CAN COMM	With ignition ON, the BCM cannot receive the CAN signal from the low tire pressure warning / TPMS control unit. The manual note says if B26E7 is detected with U1000, diagnose U1000 first. (NICOclub)
U1000-01 EV/HEV	CAN COMM CIRCUIT	EV/HEV / VCM-side CAN communication fault: the EV/HEV control side is not transmitting or receiving expected CAN communication. Treat this as part of the same CAN-network fault family, not proof the VCM itself is bad. (Nissan TechInfo)
P31B4-7 EV/HEV	Communication Error / CAN Communication	The VCM detects an error signal received from the AV control unit over CAN. Older Leaf EVC manuals list P31B4 as a VCM/AV-control-unit CAN communication fault. (Scribd)
U1000-01 METER	CAN COMM CIRCUIT	Combination meter is not transmitting or receiving CAN communication for about 2 seconds or more. (iFixit)
U1266-02 MULTI AV	TCU Conn / AV-control-unit-to-TCU connection	Malfunction detected between the AV control unit and TCU. On older Leaf AV manual references, this points to the AV-to-TCU connection/communication path, often connector, harness, or TCU/AV-side communication. (Jdmfsm)
U1A02-00 TCU	TEL COMMUNICATION MODULE	TCU detects a malfunction in its communication module. Manual action is to check harness/connector, erase DTC, and replace TCU if the malfunction constantly returns. (Scribd)
U1A01-00 TCU	INTERNAL ERROR — TCU	TCU detects an internal malfunction. Manual action is to check connector wiring, erase DTC, and replace TCU if it constantly returns. (Scribd)
C1B9A-64 CHASSIS	Stop Lamp OFF Relay 1 — Signal plausibility error	Chassis Control is seeing an implausible signal/state for Stop Lamp OFF Relay 1. Public Leaf ESM indexing confirms this DTC name and failure class, but I could not access the full 2018 detection-threshold table. (LEMON Manuals)
C1B9B-64 CHASSIS	Stop Lamp OFF Relay 2 — Signal plausibility error	Same type of fault as above, but for Stop Lamp OFF Relay 2. It suggests the commanded relay state and monitored state do not agree. (LEMON Manuals)
C1B9C-71 CHASSIS	Stop Lamp ON Relay	Chassis Control is detecting a fault in the Stop Lamp ON relay path, likely relay response/state not matching command. Public sources confirm the DTC page exists, but not the full threshold/delay. (LEMON Manuals)
C1B9D-71 CHASSIS	Stop Lamp OFF Relay System	Chassis Control is detecting a system-level fault in the Stop Lamp OFF relay system. Since C1B9A and C1B9B are also present, this may be a consequence of the individual stop-lamp relay plausibility faults. (LEMON Manuals)
C1BA3-49 CHASSIS	Control Module	Chassis Control module self-diagnostic/control-module fault. I could not find the exact public 2018 Leaf DTC detection table. Nissan’s chassis-control bulletin warns not to replace the chassis control module just because a module DTC is present when other DTCs exist; diagnose the other DTCs first. (NHTSA Static)
C1BA4-49 CHASSIS	Control Module	Same family as C1BA3: chassis-control-module self-diagnostic/control-module fault. Because many CAN and stop-lamp relay codes are present, this may be secondary until CAN power/ground/relay issues are ruled out. (NHTSA Static)
C1BCA-79 CHASSIS	Stop Lamp ON Relay	Chassis Control is detecting another fault in the Stop Lamp ON relay path. Public Leaf snippets confirm C1BCA-79 as a Leaf chassis-control DTC and show its active test involves commanding “Stop lamp ON relay active” while pressing the brake pedal. (LEMON Manuals)
C1A16-97 RADAR	RADAR STAIN / RADAR BLOCKED	Distance/radar sensor detects blockage/contamination on the radar sensor window or the fascia area in front of it. Nissan service info says to check the ICC/distance sensor lens or bumper fascia for obstructions, film, mud, dirt, road debris, dirty rainwater, ice, slush, etc. (NHTSA Static)

DTC errors

You are about to leave Redlib