DTC P0646:00 [SKYACTIV-D 1.5]

id0102q2587900

DTC P0646:00

A/C relay circuit low input

DETECTION CONDITION

•  When the following conditions are met, PCM detects that the A/C relay voltage is approx. 0 V for a continuous 5 s:

MONITORING CONDITIONS

―  Battery voltage: 9—16 V

―  A/C relay controlled off

Diagnostic support note

•  This is an intermittent monitor (other).

•  The check engine light does not illuminate.

•  FREEZE FRAME DATA is not available.

•  Snapshot data is available.

•  DTC is stored in the PCM memory.

FAIL-SAFE FUNCTION

•  PCM restricts engine-transaxle integration control. (ATX)

POSSIBLE CAUSE

•  Front body control module (FBCM) DTC is stored

•  A/C relay malfunction

•  Front body control module (FBCM) connector or terminals malfunction

•  Short to ground in wiring harness between the following terminals:

―  Front body control module (FBCM) terminal 1C—A/C relay terminal A

―  A/C relay terminal E—PCM terminal 2AQ

•  PCM connector or terminals malfunction

•  Front body control module (FBCM) malfunction

•  PCM malfunction

DTC P0646:00	A/C relay circuit low input
DETECTION CONDITION	• When the following conditions are met, PCM detects that the A/C relay voltage is approx. 0 V for a continuous 5 s: MONITORING CONDITIONS ― Battery voltage: 9—16 V ― A/C relay controlled off Diagnostic support note • This is an intermittent monitor (other). • The check engine light does not illuminate. • FREEZE FRAME DATA is not available. • Snapshot data is available. • DTC is stored in the PCM memory.
FAIL-SAFE FUNCTION	• PCM restricts engine-transaxle integration control. (ATX)
POSSIBLE CAUSE	• Front body control module (FBCM) DTC is stored • A/C relay malfunction • Front body control module (FBCM) connector or terminals malfunction • Short to ground in wiring harness between the following terminals: ― Front body control module (FBCM) terminal 1C—A/C relay terminal A ― A/C relay terminal E—PCM terminal 2AQ • PCM connector or terminals malfunction • Front body control module (FBCM) malfunction • PCM malfunction

Diagnostic Procedure

STEP	INSPECTION		ACTION
1	RECORD VEHICLE STATUS AT TIME OF DTC DETECTION TO UTILIZE WITH REPEATABILITY VERIFICATION Note • Recording can be facilitated using the screen capture function of the PC. • Record the snapshot data on the repair order.	—	Go to the next step.
2	VERIFY RELATED SERVICE INFORMATION AVAILABILITY • Verify related Service Information availability. • Is any related Service Information available?	Yes	Perform repair or diagnosis according to the available Service Information. • If the vehicle is not repaired, go to the next step.
2		No	Go to the next step.
3	CONFIRM FRONT BODY CONTROL MODULE (FBCM) DTC • Perform the front body control module (FBCM) DTC inspection using the M-MDS. (See DTC INSPECTION [FRONT BODY CONTROL MODULE (FBCM)].) • Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [FRONT BODY CONTROL MODULE (FBCM)].)
3		No	Go to the next step.
4	INSPECT A/C RELAY • Switch the ignition off. • Remove the A/C relay. (See RELAY LOCATION.) • Inspect the A/C relay. (See RELAY INSPECTION.) • Is there any malfunction?	Yes	Replace the A/C relay, then go to Step 9. (See RELAY LOCATION.)
4		No	Go to the next step.
5	INSPECT FRONT BODY CONTROL MODULE (FBCM) CONNECTOR CONDITION • Disconnect the front body control module (FBCM) connector. • Inspect for poor connection (such as damaged/pulled-out pins, corrosion). • Is there any malfunction?	Yes	Repair or replace the connector and/or terminals, then go to Step 9.
5		No	Go to the next step.
6	INSPECT A/C RELAY CIRCUIT FOR SHORT TO GROUND • Verify that the A/C relay is removed. • Verify that the front body control module (FBCM) connector is disconnected. • Inspect for continuity between the following terminals (wiring harness-side) and body ground: ― A/C relay terminal A ― A/C relay terminal E • Is there continuity?	Yes	Disconnect the PCM connector and inspect the wiring harness for short to ground. • If the short to ground circuit could be detected in the wiring harness: ― Refer to the wiring diagram and verify whether or not there is a common connector between the following terminals: • Front body control module (FBCM) terminal 1C—A/C relay terminal A • A/C relay terminal E—PCM terminal 2AQ If there is a common connector: • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground. • Repair or replace the malfunctioning part. If there is no common connector: • Repair or replace the wiring harness which has a short to ground. • If the short to ground circuit could not be detected in the wiring harness: ― Replace the PCM (short to ground in the PCM internal circuit). (See PCM REMOVAL/INSTALLATION [SKYACTIV-D 1.5].) Go to Step 9.
6		No	Go to the next step.
7	INSPECT PCM CONNECTOR CONDITION • Disconnect the PCM connector. • Inspect for poor connection (such as damaged/pulled-out pins, corrosion). • Is there any malfunction?	Yes	Repair or replace the connector and/or terminals, then go to Step 9.
7		No	Go to the next step.
8	INSPECT FRONT BODY CONTROL MODULE (FBCM) • Inspect the front body control module (FBCM). (See FRONT BODY CONTROL MODULE (FBCM) INSPECTION.) • Is there any malfunction?	Yes	Replace the front body control module (FBCM), then go to the next step. (See FRONT BODY CONTROL MODULE (FBCM) REMOVAL/INSTALLATION.)
8		No	Go to the next step.
9	VERIFY DTC TROUBLESHOOTING COMPLETED • Always reconnect all disconnected connectors. • Clear the DTC from the PCM memory using the M-MDS. (See CLEARING DTC [SKYACTIV-D 1.5].) • Start the engine. • Turn the air conditioner on and off. • Perform the DTC Reading Procedure. (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-D 1.5].) • Is the same DTC present?	Yes	Repeat the inspection from Step 1. • If the malfunction recurs, replace the PCM. (See PCM REMOVAL/INSTALLATION [SKYACTIV-D 1.5].) Go to the next step.
9		No	Go to the next step.
10	VERIFY AFTER REPAIR PROCEDURE • Perform the “AFTER REPAIR PROCEDURE”. (See AFTER REPAIR PROCEDURE [SKYACTIV-D 1.5].) • Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [SKYACTIV-D 1.5].)
10		No	DTC troubleshooting completed.