IBMobile

ASD Relay Controlled Lift Pump If the ECM is no longer powering the electric lift pump and you’re using a manual switch wired directly to the fuel pump relay for control there is a danger of the fuel pump feeding a fire in the event of an accident even if the engine stalls. The automatic shutdown relay is an alternative that will turn the fuel lift pump off if the engine stops and still be able to prime the VP44 if needed. The automatic shutdown relay (ASD) in the power distribution center (PDC) is energized by the powertrain control module (PCM) by grounding pin 85 of the relay when the engine is started. This closes the contacts and battery voltage is supplied to terminal 87 of the relay. The terminal 87 of the ASD relay supplies power to the PCM through a 14 gauge dark green/orange (DG/OR) wire. When the engine stalls the PCM opens the grounding circuit within 3 seconds and the voltage is removed from terminal 87. The lift pump relay can be controlled by connecting a wire between terminal 87 of the ASD relay, or splicing into the DG/OR wire) and terminal 86 of the lift pump relay. The power draw of the lift pump relay solenoid is less than 1 amp so an 18 gauge wire can be used. There is an option to run the lift pump without the engine on, a bypass switch and second relay can be installed. The second relay is used to isolate the PCM and not power up systems unless the key is in the on position. Also if the bypass switch was wired directly to pin #86 of the fuel pump relay the amp draw from the PCM would blow the 3 amp fuse. If installed improperly the lift pump could stay on in the event of an accident. Installer/user assumes responsibility for proper installation and use. Written by: J. Daniel Martin, Martin’s Mobile Maintenance AKA: IBMOBILE 3/24/19

Grid Heater Bypass Installing this bypass will allow you to manually control if and for how long you want to run the grid heaters when the ECM is commanding the grid heaters on. This will reduce the load on the alternator/charging system and in turn reduce the harmful AC voltage. This bypass will also keep the fault codes P0380 Intake Air Heater Relay #1 Control Circuit and P0382 Intake Air Heater Relay #2 Control Circuit from being set. Parts needed: 1. 2 micro relays, terminal 87 (5) normally open (NO) with suppressor 2. 2 5 watt / 20 ohm resistor 3. 1 single pole single throw switch (spst) 4. 2 male bullet and 2 female bullet connectors 5. 2 ring terminals 7. Rosin core solder 6. 10 female quick connect terminals 8. Heat shrink 9. ¼” protective wire cover 10. Electrical tape 11. Wire 18 AWG 4 different colors would be nice. 12. Optional 3 ATC fuse holders with 2 amp fuse 13. Something to mount the relays and resistors on. 14. 5 or more 6” zip ties Micro relay Putting it together To mount the relays, resistors and fuses I used part of a used relay mount from a Volvo that I found. It was cut and modified to fit the parts. I didn’t want to cut the wire harness at the fire wall to access the solenoid trigger wires, yellow/black and orange/black, that goes from the Engine Control Module (ECM) to the grid heater control solenoids. I ran two wires to each solenoid connecting to the trigger wires with the male bullet connectors. This sent the trigger signal back to the control relays at terminal 30 (3). Two more wires were run from terminal 87 (5) of the control relay back to terminal 86 of the grid heater solenoids and connected the wires with the female bullet connectors. You can cover the wires from the firewall to the solenoids with the ¼” protective wire cover. I installed the rely/resistor housing under the dash secured with a sheet metal screw and attached the ground wires to the dash sheet metal. For power I tapped into the fuse box on the left side of the dash and installed one of the ATC fuse holders and a 3 amp fuse. The control switch is installed into the left side of the steering column cover; I didn’t want it sticking out of the dash. With the switch in the on position the control relay contacts 30 and 87 close and the grid heaters will operate normally giving heated air to the cylinders. The switch in the off position the control relay contacts 30 and 87a are closed and the ECM signal goes to the resistors mimicking the grid heater solenoids. No check engine light and reduced electrical load on the charging system. The switch can be operated on or off before during or after engine start up. Another added benefit is if your batteries are weak the grid heaters can be turned off saving power for the starter. Written by: J. Daniel Martin, Martin’s Mobile Maintenance AKA IBMobile 12/21/2018