1. The orange and grey wires from the oil pressure switch was used to activate the fuel pump in parallel with the TBI ECM's fuel pump relay. The orange wire goes to fused battery power, the grey wire went to the fuel pump. Your 5.3L will not need these wires anymore so you can just toss the connector and trim the orange wire back to the splice in the harness.
I would like retain the stock oil pressure sending unit and guage. By leaving the tan wire only in the connector and plugging it back into the sending unit, would i be good to go? This motor had the oil pressure sending unit/oil pressure fuel switch in one.
Yup -- Just thread the stock combo back into the head and leave the tan wire hooked up to the gauge.
2. Where does this wire exit the harness? Behind the engine?
I dont remember now. I'll check it in the morning.
Ok.
3. Put a crimp on ring end onto this wire and ground it if it is infact a ground. The 5.3L harness has it's own grounding and shouldn't require any splicing into your truck's original harness. Be sure it is a ground by checking resistance to ground with a multimeter. If it is around 1 or 2 ohms, then ground it.
So if its 1-2 ohms i need to ground it? What if i come up with a different reading? Would it mean that it is already grounded?
If it comes up to more than that, it probably runs through something on it's way to ground. Most likely just a ground wire though!
If in doubt, trace it out!
4. Pink wires with a black stripe are always ignition wires. You can feed this wire into your 5.3L harness on the ignition input wire.
The dude that hooked me up the harness told me to use my old coil wire to do this sense its a heavy guage wire that originally went to the coil. Does that sound ok to do that and get rid of this wire?
Yup, the coil wire is your best best for the ignition feed.
5. Yup, your TBI ECM wanted to know when the starter solenoid was activated. The 5.3L doesn't care.
6. I don't recall what this particular wire is used for... I'll look into it.
7. If this is the wire from your HVAC controls, it will be fed into the new PCM to control the AC compressor.
I plan on either retrofitting my old compressor or using a sanden pump. Can i just wire it off the truck and leave the ecm out of it? Or will i need to let it know that the ac has been activated?
The PCM will adjust the idle when the A/C has been activated, it needs to know. The A/C controls are all in C2 (Red connector).
Pin 43 - Clutch Relay Control (provides ground for the relay coil)
Pin 55 - Low Pressure Switch (switched ground signal)
Pin 11 - Automatic Recirc Switch (switched ground signal)
Pin 17 - AC Request Signal (switched ground signal from your HVAC controls)
The High Pressure Cut Out Switch goes in between the HVAC Controls and pin 17
8. Delete this wire, the 5.3L controls AC different than the older trucks and all new engine wiring will be required.
Kinda the same as 7.
Same here!
9. As mentioned in 1. delete this wire and the oil pressure switch.
10. If your harness comes with VSS wiring, then go ahead and pull these wires right out. If not, you'll need them to tie into the PCM. You can delete the DRAC under the dash as well. The PCM handles that now.
Sorry, this one was actually TSS wire. timing by pass deal.
Timing disconnect wire = deleted!
11. This is a battery power source. One lead goes to the fuel pump relay, one to the pressure switch and the smaller ones go up to the old ECM. You'll need to power the PCM with this feed.
Dude also gave me instructions to power the pcm with the junction block on the fire wall. What say you?
The two thick feeders going into the cab through the firewall junction block are the feeders to the ignition switch. You can just pull a battery feed off the smaller junction block up on the firewall by the wiper switch or straight off the starter solenoid. Make sure you install fusible links!
12. This is the fuel pump feed wire. One goes to the ECM in the TBI harness, one goes to the fuel pump, one goes to the pressure switch. The other side goes back to the fuel pump. You'll only need one run up to the fuel pump relay.
So after all the clipping, one wire should remain and it should run down along the frame rail and should be the one that is one the side opposite my hand right?
Yup, just one grey wire that runs from the fuel pump relay back to the fuel pump.
13. Yup, delete.
14. The 5.3L won't have an output for the TH400. You'll need to hook this wire up a 12V ignition source (pink/blk wires) so the TH400 will downshift properly.
So is my understanding that this A7 was a signal sent out by the ecm telling the realy to switch and therefore tell the trans to kick down incorrect? Or is this wire simply letting the ecm know that the tranny is set to down shift?
From the looks of things, it was just a power source for the kick down switch... The ECM may have switched that supply off now and then to prevent a downshift for whatever reason. I have never actually dealt with a TBI / TH400 truck before, so some more research may not be a bad idea on this point.
15. If that plug is the clear one just to the left of the ECM, it contains the SES light, park / neutral signal, speed signal from the DRAC, ALDL wire, etc.
16. If your PCM is programmed to handle a manual transmission, then nope! If not, then it will need to be hooked up. This should be grounded when the truck is in park or neutral.
I will have to ask but i think its set for manual so i will just leave it alone for now.
Good idea!
17. Yup, hook this wire right up to the new 5.3L harness. Both the TBI ECM and the Gen III PCM provide the ground for the light.
18. This one is a ground supply to the old ECM. Just clip this wire or ground it as the new harness should provide it's own grounding.
19. Delete this wire. It runs from the DRAC and carries a 2k ppm signal to the old TBI ECM. You will need to run a new wire from the PCM up to your speedometer and install a pull up resistor circuit to have the factory speedometer work properly.
20. Orange would be battery power. I am not 100% what the white wire would have been...
I forgot what they were but i remember knowing that they were obviously not needed. Oh i think one was serial data. obviously not needed anymore...
Uh, yup! You'll want an OBDII port for scanning in the future! You can just un-pin the ALDL port and pin the OBDII port to put in it's place. You can use the ALDL wiring, the OBDII port only requires a ground, battery power source and the serial data wire from the PCM
I would like retain the stock oil pressure sending unit and guage. By leaving the tan wire only in the connector and plugging it back into the sending unit, would i be good to go? This motor had the oil pressure sending unit/oil pressure fuel switch in one.
Yup -- Just thread the stock combo back into the head and leave the tan wire hooked up to the gauge.
2. Where does this wire exit the harness? Behind the engine?
I dont remember now. I'll check it in the morning.
Ok.
3. Put a crimp on ring end onto this wire and ground it if it is infact a ground. The 5.3L harness has it's own grounding and shouldn't require any splicing into your truck's original harness. Be sure it is a ground by checking resistance to ground with a multimeter. If it is around 1 or 2 ohms, then ground it.
So if its 1-2 ohms i need to ground it? What if i come up with a different reading? Would it mean that it is already grounded?
If it comes up to more than that, it probably runs through something on it's way to ground. Most likely just a ground wire though!
If in doubt, trace it out!4. Pink wires with a black stripe are always ignition wires. You can feed this wire into your 5.3L harness on the ignition input wire.
The dude that hooked me up the harness told me to use my old coil wire to do this sense its a heavy guage wire that originally went to the coil. Does that sound ok to do that and get rid of this wire?
Yup, the coil wire is your best best for the ignition feed.
5. Yup, your TBI ECM wanted to know when the starter solenoid was activated. The 5.3L doesn't care.
6. I don't recall what this particular wire is used for... I'll look into it.
7. If this is the wire from your HVAC controls, it will be fed into the new PCM to control the AC compressor.
I plan on either retrofitting my old compressor or using a sanden pump. Can i just wire it off the truck and leave the ecm out of it? Or will i need to let it know that the ac has been activated?
The PCM will adjust the idle when the A/C has been activated, it needs to know. The A/C controls are all in C2 (Red connector).
Pin 43 - Clutch Relay Control (provides ground for the relay coil)
Pin 55 - Low Pressure Switch (switched ground signal)
Pin 11 - Automatic Recirc Switch (switched ground signal)
Pin 17 - AC Request Signal (switched ground signal from your HVAC controls)
The High Pressure Cut Out Switch goes in between the HVAC Controls and pin 17
8. Delete this wire, the 5.3L controls AC different than the older trucks and all new engine wiring will be required.
Kinda the same as 7.
Same here!
9. As mentioned in 1. delete this wire and the oil pressure switch.
10. If your harness comes with VSS wiring, then go ahead and pull these wires right out. If not, you'll need them to tie into the PCM. You can delete the DRAC under the dash as well. The PCM handles that now.
Sorry, this one was actually TSS wire. timing by pass deal.
Timing disconnect wire = deleted!
11. This is a battery power source. One lead goes to the fuel pump relay, one to the pressure switch and the smaller ones go up to the old ECM. You'll need to power the PCM with this feed.
Dude also gave me instructions to power the pcm with the junction block on the fire wall. What say you?
The two thick feeders going into the cab through the firewall junction block are the feeders to the ignition switch. You can just pull a battery feed off the smaller junction block up on the firewall by the wiper switch or straight off the starter solenoid. Make sure you install fusible links!
12. This is the fuel pump feed wire. One goes to the ECM in the TBI harness, one goes to the fuel pump, one goes to the pressure switch. The other side goes back to the fuel pump. You'll only need one run up to the fuel pump relay.
So after all the clipping, one wire should remain and it should run down along the frame rail and should be the one that is one the side opposite my hand right?
Yup, just one grey wire that runs from the fuel pump relay back to the fuel pump.
13. Yup, delete.
14. The 5.3L won't have an output for the TH400. You'll need to hook this wire up a 12V ignition source (pink/blk wires) so the TH400 will downshift properly.
So is my understanding that this A7 was a signal sent out by the ecm telling the realy to switch and therefore tell the trans to kick down incorrect? Or is this wire simply letting the ecm know that the tranny is set to down shift?
From the looks of things, it was just a power source for the kick down switch... The ECM may have switched that supply off now and then to prevent a downshift for whatever reason. I have never actually dealt with a TBI / TH400 truck before, so some more research may not be a bad idea on this point.
15. If that plug is the clear one just to the left of the ECM, it contains the SES light, park / neutral signal, speed signal from the DRAC, ALDL wire, etc.
16. If your PCM is programmed to handle a manual transmission, then nope! If not, then it will need to be hooked up. This should be grounded when the truck is in park or neutral.
I will have to ask but i think its set for manual so i will just leave it alone for now.
Good idea!
17. Yup, hook this wire right up to the new 5.3L harness. Both the TBI ECM and the Gen III PCM provide the ground for the light.
18. This one is a ground supply to the old ECM. Just clip this wire or ground it as the new harness should provide it's own grounding.
19. Delete this wire. It runs from the DRAC and carries a 2k ppm signal to the old TBI ECM. You will need to run a new wire from the PCM up to your speedometer and install a pull up resistor circuit to have the factory speedometer work properly.
20. Orange would be battery power. I am not 100% what the white wire would have been...
I forgot what they were but i remember knowing that they were obviously not needed. Oh i think one was serial data. obviously not needed anymore...
Uh, yup! You'll want an OBDII port for scanning in the future! You can just un-pin the ALDL port and pin the OBDII port to put in it's place. You can use the ALDL wiring, the OBDII port only requires a ground, battery power source and the serial data wire from the PCM
