DTC B1229 or DTC indicator E and AUTO: An Open in the Sunlight Sensor Circuit

WARNING: This page is about a different car, the 2013 Acura MDX, 2012 Acura MDX, 2011 Acura MDX, and 2010 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

Clear the DTCs with the HDS.
Turn the ignition switch to LOCK (0) and then back to ON (II).
Do the self-diagnostic function with the HDS (see HOW TO USE THE SELF-DIAGNOSTIC FUNCTION WITH THE HDS ) or the climate control unit (see HOW TO USE THE SELF-DIAGNOSTIC FUNCTION WITHOUT THE HDS ).
Check for DTCs.
Is DTC B1229 or E and AUTO indicated?

YES -Go to step 5.

NO -Intermittent failure, check for loose wires or poor connections in the sunlight sensor circuit.
Turn the ignition switch to LOCK (0).
Disconnect the sunlight sensor 5P connector.
Disconnect climate control unit connector A (40P).
Check for continuity between climate control unit connector A (40P) terminal No. 29 and sunlight sensor 5P connector terminal No. 4.

Fig 1: Checking For Continuity Between Climate Control Unit Connector A (40P) Terminal No. 29 And Sunlight Sensor 5P Connector Terminal No. 4
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 9.

NO -Repair an open in the wire between the climate control unit and the sunlight sensor.
Check for continuity between climate control unit connector A (40P) terminal No. 8 and sunlight sensor 5P connector terminal No. 2.

Fig 2: Checking For Continuity Between Climate Control Unit Connector A (40P) Terminal No. 8 And Sunlight Sensor 5P Connector Terminal No. 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 10.

NO -Repair an open in the wire between the climate control unit and the sunlight sensor.
Reconnect the sunlight sensor 5P connector.
Reconnect climate control unit connector A (40P).
Test the sunlight sensor (see SUNLIGHT SENSOR TEST ).
Is the sunlight sensor OK?

YES -Check for loose wires or poor connections at climate control unit connector A (40P) and at the sunlight sensor 5P connector. If the connections are good, substitute a known-good climate control unit, and recheck. If the symptom/indication goes away, replace the original climate control unit (see CLIMATE CONTROL UNIT REMOVAL/INSTALLATION ).

NO -Replace the sunlight sensor (see SUNLIGHT SENSOR REPLACEMENT ).