Just like you, we see our share of new and unique vehicle problems. The 5 Fast Fixes below are examples of some recent head scratchers that we worked through with customers on our Repair Hotline.
These short-cut tests and confirmed fixes are now at your fingertips along with more than 600,000 Hotline Archives in Direct-Hit.
2005 Nissan Quest Base 3.5L, V6, MFI, DOHC, Eng Desg VQ35DE
Sometimes the Air Conditioning (A/C) compressor clutch engages and the A/C works fine and sometimes the A/C compressor clutch does not engage. Scan tool shows A/C off in the Engine Control Module (ECM), the Body Control Module (BCM), and the Intelligent Power Distribution Module (IPDM) when the A/C is inoperative. The ambient temperature display in the dash shows -40 degrees when the A/C will not work. Has a totaled 2005 Quest (fleet vehicle) that he has been swapping parts out with and no help - has swapped the ambient sensor, the intake sensor and the refrigerant pressure sensor. The refrigerant pressure sensor reads 0.9 volts A/C off and jumped power to the A/C compressor clutch and the clutch engaged and A/C worked fine and the pressure sensor voltage read normally. Engine temperature reads normally in the ECM.
1. Backprobe and check the voltage on the Gray/Red wire at the ambient sensor and look for about 2.5 - 3.5 volts or so depending on how cold it is outside. The colder it is, the higher the voltage reading.
2. If the ambient sensor voltage reads near 5 volts, backprobe and check the ambient sensor ground on the Orange/Black wire and look for 0.05 volts or less. The ambient sensor inputs to the front air control on the Gray/Red wire in terminal 17 of the front air control.
3. Backprobe and check the A/C request input to the BCM on the Blue/Red wire in terminal 12 of the front air control. The front air control should ground the Blue/Red wire in terminal 12 when the A/C is turned on, so look for near 0 volts. See what the voltage reads when the A/C is inoperative.
4. If the Blue/Red wire in terminal 12 of the front air control reads 5 or 12 volts when the A/C is inoperative, try grounding the Blue/Red wire and see if the A/C turns on. If so, it would be known that the BCM, ECM and IPDM are working and will need to focus on the front air control and the inputs to it.
Ambient Sensor Wiring
Repaired Ambient Sensor Wiring: Replaced the 5 volt reference line for the ambient air temperature sensor.
A Central Processing Unit (CPU) inside the IPDM controls the ground for the A/C relay to supply battery voltage to the A/C compressor clutch. The ECM and the BCM communicate on Controller Area Network (CAN) to the CPU inside the IPDM to command the A/C on.
2010 Lincoln Navigator Base 5.4L, V8, MFI, SOHC, VIN 5
The blower motor for the rear system is inoperative. There is no power to the blower. The front system works normally.
1. Verify fuse #34 30A in the Battery Junction Box (BJB) is present and has full battery voltage on both sides at all times.
2. If the fuse is OK and there is no voltage to the rear blower motor on the Brown/White (BN/WH) wire, access the Auxiliary Relay Box #2 behind the Right Hand (RH) trim panel in the cargo area. See the attached documents for the location and the relay labeling in the box.
3. At Auxiliary Blower Motor Relay #1, check for battery voltage on the Yellow/Red (YE/RD) wire from fuse #34. Check for battery voltage on the White/Blue (WH/BU) wire with key on from fuse #46 in the Smart Junction Box (SJB) (interior fuse panel). Check for a ground on the Violet/White (VT/WH) wire from the Dual Automatic Temperature Control (DATC) module. Lastly, check for battery voltage out of the relay on the BN/WH wire. If all inputs are OK but no voltage out, swap the relay with another relay and recheck. If there is now battery voltage out and the blower operates, replace the relay. Otherwise, repair any of the wires as needed and recheck operation.
Auxiliary Blower Motor Relay #1
Auxiliary Blower Motor Relay #1 Wiring
Replaced Auxiliary Blower Motor Relay #1: Replaced the relay, then had to disconnect the battery to reset the DATC module before it would turn the relay on.
2008 Porsche Cayenne S 4.8L, V8, MFI, DOHC, VIN B, Eng Desg M48.01
After replacing the high pressure fuel pump there is no pressure increase at all.
1. When replacing the high pressure pump, pay attention to the coupler that is between the pump and the cam. It can fall out or stick to the old pump.
2. Failure to install this part will cause the pump to not be mechanically driven.
Missing High Pressure Pump Coupler
Installed High Pressure Pump Coupler
2005 Chevrolet Silverado 2500 HD Base 6.0L, V8, MFI, OHV, VIN U
Code P0622. An add-on battery isolator is installed between the PCM and alternator. The vehicle used to be a railroad truck and the charging system is not charging.
1. Contact the manufacturer that makes the device for technical information. Inspect wiring and connections carefully.
2. Bypass the isolator for test purposes and see if the alternator charges and the code clears.
Failed Add On Battery Isolator
Replaced Add On Battery Isolator
2009 Subaru Outback 2.5i Limited 2.5L, H4, MFI, SOHC, Eng Desg EJ253
Security light comes on steady the second you insert the key. Only cranks 1 second then quits cranking. Replaced engine, battery has been unhooked 1 month. Hooked up and started acting this way. Replaced instrument cluster.
1. Were you given the correct key when the car was towed in for the bad engine? Did it ever run for you with that key? Have the customer bring you all the keys to test.
2. If the security light is on solid, there has been an immobilizer/security event.
Look for codes P05xx or P15xx or B14xx.
3. Have the immobilizer system reprogrammed by a locksmith.
Performed Immobilizer Registration
We'll continue to give you a heads-up on new vehicle issues we're helping to solve on our Hotline with 5 Fast Fixes every other week.
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