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412-02-25 412-02-25 Heating and Ventilation DIAGNOSIS AND TESTING (Continued) PINPOINT TEST P: NO HEAT/INSUFFICIENT HEAT TEST STEP ACTION TO TAKE P1 CHECK POSITIVE TEMPERATURE COEFFICIENT (PTC) HEATER CORE CONTROL SIGNALS • Connect 104-Pin Breakout Box (BOB) to interface adapter assembly Yes = GO to P3. (IAA) module and IAA module C1945. • With key ON, set the mode select knob to the PANEL/FLOOR position No = If voltage equals 0 volts, and the temperature control knob to the full warm position, and monitor REPLACE the IAA module. IAA module PIDs CORE A and CORE B. • Note which PID indicates ON. • If CORE A PID indicates ON, measure the voltage between BOB pin If voltage is greater than 4.5 33 and ground (BOB pin 80). volts, GO to P2. • If CORE B PID indicates ON, measure the voltage between BOB pin 34 and ground (BOB pin 80). • Is the voltage between 2 and 3 volts? P2 CHECK CIRCUIT 3260 (O/W) FOR OPEN • With key OFF, disconnect PTC switching module C1999 and measure Yes = REPLACE the PTC the resistance of the O/W wire between pin 4 on PTC switching module switching module. C1999 and BOB pin 33. • Is the resistance less than 5 ohms? No = REPAIR the O/W wire. P3 CHECK PTC HEATER CORE CONTROL SIGNALS AFTER CYCLING IGNITION KEY • Turn the ignition key to the OFF position and then to the ON position. Yes = System OK. CHECK wiring for intermittent connections. • With key ON, set the mode select knob to the PANEL/FLOOR position No = If voltage equals 0 volts, and the temperature control knob to the full warm position, and monitor REPLACE the IAA module. IAA module PIDs CORE A and CORE B. REFER to • Note which PID indicates ON. • If CORE A PID indicates ON, measure the voltage between BOB pin If voltage is greater than 4.5 33 and ground (BOB pin 80). volts, GO to P4. • If CORE B PID indicates ON, measure the voltage between BOB pin 34 and ground (BOB pin 80). • Is the voltage between 2 and 3 volts? P4 CHECK CIRCUIT 3261 (PK/Y) FOR OPEN • With key OFF, disconnect PTC switching module C1999 and measure Yes = REPLACE the PTC the resistance of the PK/Y wire between pin 5 on PTC switching module switching module. C1999 and BOB pin 34. • Is the resistance less than 5 ohms? No = REPAIR the PK/Y wire. PINPOINT TEST Q: VACUUM PUMP CYCLES ON AND OFF WITHOUT BRAKE PEDAL ACTIVATION TEST STEP ACTION TO TAKE Q1 CHECK SYSTEM AIRFLOW • With key ON, set the blower control knob to the HIGH position and Yes = System OK. If vacuum rotate the mode select knob through all mode positions. pump cycles on and off continuously without brake • Check the airflow through the climate control outlets for all mode No = If air flows through positions. defroster outlets for all • Does air flow through the correct outlets for all mode positions? mode positions, GO to Q2. incorrect outlets, GO to (Continued) |