Possible Causes

WARNING: This page is about a different car, the 2005 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.

high speed CAN circuits (W) and (B) shorted to ground or open
DLC D-01
PCM 0140-175b
instrument cluster
PCM
PCM or instrument cluster termination resistors

POWERTRAIN CONTROL MODULE (PCM) DOES NOT RESPOND TO DIAGNOSTIC TOOL - DIAGNOSTIC PROCEDURE

PINPOINT TEST 1		THE POWERTRAIN CONTROL MODULE (PCM) DOES NOT RESPOND TO THE DIAGNOSTIC TOOL
STEP	INSPECTION		ACTION
1	CHECK THE HIGH SPEED CAN CIRCUITS BETWEEN THE PCM AND THE DLC FOR AN OPEN Key OFF. Disconnect the PCM 0140-175b/275b. Measure the resistance between the PCM 0140-175b/275b pin 11, circuit (W), harness side and the DLC D-01 pin 6, circuit (W), harness side; and between the PCM 0140-175b/275b pin 23, circuit (B), harness side and the DLC D-01 pin 14, circuit (B), harness side. Are the resistances less than 5 ohms?	Yes	Go to next step.
1		No	REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.
2	CHECK FOR CORRECT PCM OPERATION Disconnect all the PCM connectors. Check for: corrosion pushed-out pins Connect all the PCM connectors and make sure they seat correctly. Operate the system and verify the concern is still present. Is the concern still present?	Yes	DIAGNOSE the high speed CAN. See PINPOINT TEST 8: NO MODULE/NETWORK COMMUNICATION - NO POWER TO THE DIAGNOSTIC TOOL .
2		No	The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.