DTC U0101-00

DTC U0101-00 : Lost Communication With the PCM (PGM-FI system)

NOTE:

Before doing this troubleshooting procedure, find out if the vehicle was in a collision. If so, verify that all the required components were replaced with new components, of the correct part number, and that they were properly installed .
Before doing this troubleshooting procedure, review SRS Precautions and Procedures , General Troubleshooting Information , and Battery Terminal Disconnection and Reconnection .
Before replacing the SRS unit, check the SRS unit software version with the HDS. If the software version is not the latest, update the SRS unit software , and retest.

DTC Description	DTC
U0101-00 Lost communication with the PCM (PGM-FI system)

DTC (SRS)

Body electrical system check

-1. Check for any F CAN and B CAN communication DTCs with the HDS.

DTC Description	DTC

Are there any communication DTCs?

YES

Go to the appropriate DTC troubleshooting.

Go to step 2.

DTC check

-1. Clear the DTCs with the HDS .

-2. Press the engine start/stop button to select the ON mode, then wait for 10 seconds.

-3. Check for DTCs with the HDS .

DTC Description	DTC
U0101-00 Lost communication with the PCM (PGM-FI system)

Is DTC U0101-00 indicated?

YES

Go to step 3.

Intermittent failure, the system is OK at this time. Go to Troubleshooting Intermittent Failures . If another DTC is indicated, troubleshoot the DTC.

PGM-FI system check
-1. Press the engine start/stop button to select the OFF mode.

-2. Start the engine, and see if the malfunction indicator lamp (MIL) also stays on.

Does the MIL stay on longer than 30 seconds?

YES

Go to the Fuel and Emissions Systems General Troubleshooting Information .

NO

Go to step 4.

Open wire check (F CAN-H, F CAN-L lines)

-1. Press the engine start/stop button to select the OFF mode.

-2. Jump the SCS line with the HDS, and wait more than 1 minute.

SCS short

NOTE: This step must be done to protect the PCM from damage.

-3. Disconnect the following connector.

Disconnect PCM connector A (51P)

-4. Disconnect the negative cable from the battery, then wait at least 3 minutes.

-5. Disconnect the following connector.

SRS unit connector A (39P)

-6. Check for continuity between test points 1 and 2.

Test condition	OFF mode
	PCM connector A (51P): disconnected
	SRS unit connector A (39P): disconnected
Test circuit	F CAN-H
Test point 1	SRS unit connector A (39P) No. 20
Test point 2	PCM connector A (51P) No. 2 (WHT)

Test circuit	F CAN-L
Test point 1	SRS unit connector A (39P) No. 21
Test point 2	PCM connector A (51P) No. 3 (RED)

Courtesy of HONDA, U.S.A., INC.

Is there continuity?

YES

The F CAN-H and F CAN-L wires are OK. Faulty SRS unit or poor connection at SRS unit connector A (39P) and the SRS unit. Check the connection; if the connection is OK, replace the SRS unit . If the DTC does not clear, replace the engine compartment wire harness or the dashboard wire harness.

Open in the harness between SRS unit connector A (39P) terminal No. 20 and PCM connector A (51P) terminal No. 2, or between SRS unit connector A (39P) terminal No. 21 and PCM connector A (51P) terminal No. 3 (engine compartment wire harness or dashboard wire harness); replace the faulty harness, then clear the DTC.