2002 1500 5.3L. So many things could have caused these problems and i will try to put it all out there. The truck is rusty and salt found its way in the fuse block. Strange things happen to the dash and lights and the horn. Now I have the truck torn apart. Box, doors, fenders, etc. are off. I unplugged the cables from the back of the fuse block. Cleaned it with a soda blaster and washed it with a pressure washer. Hung it up to dry. Installed it back in the truck and the fuel pump was without power. Here's where it gets hard to track the order. The relay wasn't getting power. I jumped the relay and the pump ran. The truck ran normally but not for long. Jumping the jumper stopped working. No connection between the relay side of pin 87 and the wire to the fuel pump. I used an ohmmeter to use the window defogger- new location for relay. I swaped wires around. I have dyslexia. I think they are right. Pin 30 is always hot. Pin 85 is open as it doesn't source or sink power. Pin 87 goes to the fuel pump. Pin 85 sinks power when switch is on. Now when I jump the relay, the truck runs but keeps running when I turn the key off. Where does the wire in pin 85 go? What should I expect from pin 85? Do I have the wires in the right place? I dont know if there is a more difficult way to do this. Thanks Creeplebod
creeplebod
This is a generic GM fuel pump relay diagram. It isn't specific to your truck but I think it is correct for what you are wanting to know. The wire colors may not be the same as yours.
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Tennman, I was told that the PCM is supposed to sink the power and the key switch was the supply. The key is turned on and pin 86 is 12 volts. Pin 85 goes low to 1 or 2 volts for a couple seconds (engine not running) and stops letting the voltage float to 12 volts shutting off the fuel pump. I found a green/white wire at the PCM. I can't trace it with a VOM at the fuse block. The green/white wire sinks power to ground with the VOM but the load of the relay pulls it back up to 12 volts. If the diagram above is what I have, Pull the relay and the green/white wire is dead.
Creeplebod
Creeplebod
Tennman,
I saw a utube video that supports that the PCM sinks power. I saw 2 other diagrams similar to what you posted that shows the PCM sources the fuel pump relay. Pin 85 is hot when he key is on regardless if the engine is running or how long the key is on. Grounding pin 86 the pump will run whenever the key is on. I don't know how the pump would stop after the key is on for 3 seconds and engine not running. Something here is wrong. Either pin 86 has the wrong feed (not coming from the PCM) or something burned out in the PCM not sinking enough power from pin 85. What pin does the green/white wire contact on the PCM? A diagram showed the pinout of the PCM with pin 9 red controls the fuel pump. Pin 9 on my PCM has a pink wire. Pin 8 has a green/white wire but won't do what is needed to control the relay. I don't have continuity between the green/white wire (pin 9) to the fuse block. Also shows pin 3 to control the secondary fuel pump. I assume that is for trucks with duel tanks. I need to trace these wires more closely. I don't know what to look for next. Any ideas?
I saw a utube video that supports that the PCM sinks power. I saw 2 other diagrams similar to what you posted that shows the PCM sources the fuel pump relay. Pin 85 is hot when he key is on regardless if the engine is running or how long the key is on. Grounding pin 86 the pump will run whenever the key is on. I don't know how the pump would stop after the key is on for 3 seconds and engine not running. Something here is wrong. Either pin 86 has the wrong feed (not coming from the PCM) or something burned out in the PCM not sinking enough power from pin 85. What pin does the green/white wire contact on the PCM? A diagram showed the pinout of the PCM with pin 9 red controls the fuel pump. Pin 9 on my PCM has a pink wire. Pin 8 has a green/white wire but won't do what is needed to control the relay. I don't have continuity between the green/white wire (pin 9) to the fuse block. Also shows pin 3 to control the secondary fuel pump. I assume that is for trucks with duel tanks. I need to trace these wires more closely. I don't know what to look for next. Any ideas?
OK, I hope I don't sound disrespectful but I think you should dispense with using the terms Sinking and Sourcing to describe the results you are getting with your meter. You will only confuse a lot of auto mechanics here on the forum who would otherwise offer you some help with your problem. We should use simple automotive terms to describe test results so we are all on the same page. The following test should determine why your fuel pump won't run.
1) It seems like you have already proved in your testing that pin 30 has 12 VDC power and that when you jump pins 30 and 87 the fuel pump will run constantly. Is that correct? If so move on the step 2. If not find out why the fuel pump isn't running when you jump pins 30 and 87 before moving on to step 2.
2) Install a fuel pump relay that is know to be good. Turn the fuse block up so you can get to the terminals on the bottom. Set your meter to read ohms. Put one lead on the negative post of the battery and the other lead on terminal 86 at the base of the fuel pump relay. You should read almost 0 resistance proving that you have a good ground. If you don't have a good ground find out why before proceeding.
3) Attach a fuel pressure tester to the fuel rail. Set your meter to read 12 VDC. Put the black lead of your meter on terminal 86 and the red lead on terminal 85. While watching the meter closely, have a helper turn the key to the run (not start) position. You should observe your meter reading about 12 volts for a few seconds during the prime cycle and then drop back to 0 volts.
The fuel pump should also run and build fuel pressure to prime the fuel system and it should maintain pressure for several minutes.
Repeat the test several times by having your helper turn the key from the off position to the run position to make certain of the results of this test. (There shouldn't be a constant 12 volts to pin 85 until the engine starts running.) Are you getting the proper results when doing this test?
4) If the tests in step 3 fail, run a jumper between the positive battery post and terminal 85 and see if the fuel pump relay picks up and the fuel pump starts running. It should run until you remove the jumper. If this test is successful in the fuel pump run you could have a bad connection between the PCM and terminal 85 on the relay or possibly a bad PCM,
Hope this helps.
1) It seems like you have already proved in your testing that pin 30 has 12 VDC power and that when you jump pins 30 and 87 the fuel pump will run constantly. Is that correct? If so move on the step 2. If not find out why the fuel pump isn't running when you jump pins 30 and 87 before moving on to step 2.
2) Install a fuel pump relay that is know to be good. Turn the fuse block up so you can get to the terminals on the bottom. Set your meter to read ohms. Put one lead on the negative post of the battery and the other lead on terminal 86 at the base of the fuel pump relay. You should read almost 0 resistance proving that you have a good ground. If you don't have a good ground find out why before proceeding.
3) Attach a fuel pressure tester to the fuel rail. Set your meter to read 12 VDC. Put the black lead of your meter on terminal 86 and the red lead on terminal 85. While watching the meter closely, have a helper turn the key to the run (not start) position. You should observe your meter reading about 12 volts for a few seconds during the prime cycle and then drop back to 0 volts.
The fuel pump should also run and build fuel pressure to prime the fuel system and it should maintain pressure for several minutes.
Repeat the test several times by having your helper turn the key from the off position to the run position to make certain of the results of this test. (There shouldn't be a constant 12 volts to pin 85 until the engine starts running.) Are you getting the proper results when doing this test?
4) If the tests in step 3 fail, run a jumper between the positive battery post and terminal 85 and see if the fuel pump relay picks up and the fuel pump starts running. It should run until you remove the jumper. If this test is successful in the fuel pump run you could have a bad connection between the PCM and terminal 85 on the relay or possibly a bad PCM,
Hope this helps.
Tennman, That was a well thought out procedure to troubleshoot the relay problem. It was easy to follow. I fixed the ground issue so the relay works. The signal from the computer is not right. Switch the key on and pin 85 stays hot till the key is turned off. Start the truck and battery voltage goes to 14 volts. Pin 85 has 13.5 volts. Turn the key off and the engine keeps running with pin 85 at 10.5 volts. Pull the fuel pump relay and the truck runs another 2 seconds and stalls. 2 seconds later pin 85 goes to 0 volts. Power nust be pin 85 and the electrical system as a whole (The alternator has the battery at 14 volts) system while running with the key off. There is a relay turning off somewhere when the rest turns off. I have yet to find the relay that is clicking off first before the others. I know you need more information here but I am at a loss as what to check for. Thanks creeplebod
I believe you have the fuel pump relay working properly now. Sounds to me like you have a bad ignition switch that isn't turning off when you turn the key to the off position. Even if the fuel pump kept running for some reason when you turn the key off, the ignition coil should lose power when you turn the key off and kill the engine. I don't think the PCM is getting a signal that the key has been turned off. That is the reason the fuel pump and the engine keeps running. Mostly just a guess on my part since I have no way testing anything but logic tells me that is what's happening.creeplebod said:
Things are getting worse. I removed the 4 plug connectors and the ignition relay from the fuse block and stuck a wire in pin 85. I used an ohmmeter to find all the contacts made to pin 85. There were several and I recorded their locations. Then I removed one of those wires from the plug (one at a time), reassembled the fuse block, and started the truck. I was hoping to find one of those wires back feeding power keeping that relay engaged. I I was on the 3rd to last wire to test when the truck wouldn't start. Now none of the relays on the fuse block gets energized. All of the wires are in where they came from. I don't know what changed or how to trace it. I downloaded and printed a schematic showing the blue plug for the PCM on the left and the red plug on the right. It does not show the key switch or much of the wiring inside the cab.I downloaded other drawings like the key switch but the wire numbers do not work with the schematic above. I will just rip out all the wires and start over 
.
.I started tracing how the PCM gets power. The red wire comes from the 20 amp fuse and the PCM is receiving it. The engine 1 10 amp fuse has no power. Left side of the fuse socket goes to E3 of the red connector behind the fuse block to a pink wire. I can't find the source for that fuse (where it goes ???). Right side goes to pin 86 of the IGN 1 relay. I ran a hot wire to the right fuse socket and the truck started. It still won't shut off by the key. I disconnected power to the fuse socket and the fuse socket was still hot. I pulled the fuel pump relay to shut down the engine. The engine stopped and 2 seconds later the fuse socket went dead.
If anyone's wiring diagram shows where the pink wire from the red connector goes, help. My drawings I downloaded shows how the PCM connects to the fuse block and sensors and some components. It doesn't show how the ignition switch fits in. I need the run wire from the key switch to which connector and the location of the actual terminal.
Thanks Creeplebod
If anyone's wiring diagram shows where the pink wire from the red connector goes, help. My drawings I downloaded shows how the PCM connects to the fuse block and sensors and some components. It doesn't show how the ignition switch fits in. I need the run wire from the key switch to which connector and the location of the actual terminal.
Thanks Creeplebod
I spent days in the dark over what RAP is. Retained accessory power that stays on for 20 minutes. I think now I have a wire crossed somewhere that keeps the engine running when the key is off. The click shutting off the ignition is coming from inside the cab. I haven't waited 20 minutes to see if it shuts off. I also don't know why the ignition circuit stays hot with the key off until the engine has stopped running for 2 seconds. Does it take that long for the oil pressure to drop far enough to trigger a warning? I wanted to stick a test lead in each wire to see what is hot or ground. Then I realized many of the circuits are connected together when the engine is running. They may be hot or grounded by a relay of switch from another circuit. Well, till I learn something else creeplebod
There should be a RAP relay that you can pull if you think that is what is keeping the engine running. That relay might be what you are hearing click inside the cab.
Well crap -- that didn't work. I printed out the wiring diagram between the fuse block, the sensors and actuators, and the computer. I had other diagrams as well. Power comes from the ignition switch to a 10 amp fuse on the fuse block. Then it goes to pin 19 on the computers blue connector. Well hell - socket 19 is empty. I need more accurate diagrams to check my wiring to know what has power and when.
I went to a garage which has access to the data base of all vehicles. Printed the wiring diagram between the computer and fuse block and the power flow block diagram throughout the truck. The mechanic there asked if I took the fuse block itself apart. There are circuits inside that may need cleaning. I told him I had tried but was afraid of breaking something. I went to a junk yard and pulled a fuse block ($15) from a truck that had a solid inner fender (no salt spray). Time to take the old one apart. Did break it but learned what I did wrong. Remove the top and bottom cover and your left with a plastic rectangle with spades sticking out of both sides. A connector fits on the spade for fuses and relays to plug in. The other side has just the spades that the cables connect to. Lift a thin plastic board and see the wires zigzagging all over. The uninsulated wires were green and a few were broken. The plastic board has clips groves that hold the wire in place. The spades has a small notch that the wire is shoved into. Pulling the board away and it pulls the wires out of the plastic clips. Putting it together is a one time thing at the factory.
I did pull the covers off the replacement fuse block looking for corrosion. 4 square headed bolts have to be pushed out Use a heat gun to soften the plastic to avoid damage to the hole. Same way for assembly.
Now I have another problem. big surprise! No power is going to the starter relay. I do hear a relay click under the dash by the door. I checked every wire going into the fuse block. None of them had power when only in start position. Most wires were dead, some always hot, some were hot on run and start and a few wires were hot only in the run position. The clicking I hear when the key is in start position was the RAD relay. It is an oddball with 5 pins, and single pole double through relay. I decided to call it quits at 2:00 and unhooked the battery. Its vary quiet at 2 in the morning. I heard that relay click when I unhooked the battery and the key was off. Doesn't seem that relay should be on 24/7. I need some ideas. Oh, more bad news, the eng1 fuse is still dead regardless of the position of the key switch.
I have never tackled something this difficult.
I did pull the covers off the replacement fuse block looking for corrosion. 4 square headed bolts have to be pushed out Use a heat gun to soften the plastic to avoid damage to the hole. Same way for assembly.
Now I have another problem. big surprise! No power is going to the starter relay. I do hear a relay click under the dash by the door. I checked every wire going into the fuse block. None of them had power when only in start position. Most wires were dead, some always hot, some were hot on run and start and a few wires were hot only in the run position. The clicking I hear when the key is in start position was the RAD relay. It is an oddball with 5 pins, and single pole double through relay. I decided to call it quits at 2:00 and unhooked the battery. Its vary quiet at 2 in the morning. I heard that relay click when I unhooked the battery and the key was off. Doesn't seem that relay should be on 24/7. I need some ideas. Oh, more bad news, the eng1 fuse is still dead regardless of the position of the key switch.
I have never tackled something this difficult.
I went to a garage which has access to the data base of all vehicles. Printed the wiring diagram between the computer and fuse block and the power flow block diagram throughout the truck. The mechanic there asked if I took the fuse block itself apart. There are circuits inside that may need cleaning. I told him I had tried but was afraid of breaking something. I went to a junk yard and pulled a fuse block ($15) from a truck that had a solid inner fender (no salt spray). Time to take the old one apart. Did break it but learned what I did wrong. Remove the top and bottom cover and your left with a plastic rectangle with spades sticking out of both sides. A connector fits on the spade for fuses and relays to plug in. The other side has just the spades that the cables connect to. Lift a thin plastic board and see the wires zigzagging all over. The uninsulated wires were green and a few were broken. The plastic board has clips groves that hold the wire in place. The spades has a small notch that the wire is shoved into. Pulling the board away and it pulls the wires out of the plastic clips. Putting it together is a one time thing at the factory.
I did pull the covers off the replacement fuse block looking for corrosion. 4 square headed bolts have to be pushed out Use a heat gun to soften the plastic to avoid damage to the hole. Same way for assembly.
Now I have another problem. big surprise! No power is going to the starter relay. I do hear a relay click under the dash by the door. I checked every wire going into the fuse block. None of them had power when only in start position. Most wires were dead, some always hot, some were hot on run and start and a few wires were hot only in the run position. The clicking I hear when the key is in start position was the RAD relay. It is an oddball with 5 pins, and single pole double through relay. I decided to call it quits at 2:00 and unhooked the battery. Its vary quiet at 2 in the morning. I heard that relay click when I unhooked the battery and the key was off. Doesn't seem that relay should be on 24/7. I need some ideas. Oh, more bad news, the eng1 fuse is still dead regardless of the position of the key switch.
I have never tackled something this difficult. I found a link that shows the wiring diagram between the computer and many of the components. Printed it out in color and taped all 10 pages together. There were some things that didn't fit or was missing. Then I found the diagram was of a 2002 5.3 engine - in a Trans Am. Can someone access the online resource for the wiring diagram and email them to me so I can print the right ones out? I think someone has to contact me if you can do it then give you my email address.
The guy at the garage said to follow the wires according to the block diagram they gave me and trace them to the ignition switch start position. I have found nothing that is hot with the key only in the start position. I removed the kick board and the steel panel under the steering column. There I found a black box with 3 different color connectors. My ohm meter is not going to work with something like that. I want to put a load on it but does a regular test light draw too much current for some systems?
I did pull the covers off the replacement fuse block looking for corrosion. 4 square headed bolts have to be pushed out Use a heat gun to soften the plastic to avoid damage to the hole. Same way for assembly.
Now I have another problem. big surprise! No power is going to the starter relay. I do hear a relay click under the dash by the door. I checked every wire going into the fuse block. None of them had power when only in start position. Most wires were dead, some always hot, some were hot on run and start and a few wires were hot only in the run position. The clicking I hear when the key is in start position was the RAD relay. It is an oddball with 5 pins, and single pole double through relay. I decided to call it quits at 2:00 and unhooked the battery. Its vary quiet at 2 in the morning. I heard that relay click when I unhooked the battery and the key was off. Doesn't seem that relay should be on 24/7. I need some ideas. Oh, more bad news, the eng1 fuse is still dead regardless of the position of the key switch.
I have never tackled something this difficult. I found a link that shows the wiring diagram between the computer and many of the components. Printed it out in color and taped all 10 pages together. There were some things that didn't fit or was missing. Then I found the diagram was of a 2002 5.3 engine - in a Trans Am. Can someone access the online resource for the wiring diagram and email them to me so I can print the right ones out? I think someone has to contact me if you can do it then give you my email address.
The guy at the garage said to follow the wires according to the block diagram they gave me and trace them to the ignition switch start position. I have found nothing that is hot with the key only in the start position. I removed the kick board and the steel panel under the steering column. There I found a black box with 3 different color connectors. My ohm meter is not going to work with something like that. I want to put a load on it but does a regular test light draw too much current for some systems?
I am still working on the electrical system of this truck. The fuel pump works now so maybe start another thread?
I changed the ignition switch and it turns over. Still not getting power to the IGN.1 fuse. I traced the pink wire that is E3 of the red plug. I'm calling it E3 as that is its position holding the fuse block upside down and the large fuses toward the engine. I am standing by the left front wheel. I know either the green or red connector is labeled in reverse to the other plugs. It is he 5th column over and 3rd row from the top (top being toward the engine. This is supposed too receive power from the ignition switch. I traced the pink wire from E3 to the evap vent solenoid. So, what wire is supposed to be in E3 and where does the pink wire supposed to go?
I was able to download a diagram of the 4 plugs with a chart saying what each wire is. This diagram does not fit my truck Can a correct table be found and made available? I don't know the original source of the diagrams I downloaded.
I changed the ignition switch and it turns over. Still not getting power to the IGN.1 fuse. I traced the pink wire that is E3 of the red plug. I'm calling it E3 as that is its position holding the fuse block upside down and the large fuses toward the engine. I am standing by the left front wheel. I know either the green or red connector is labeled in reverse to the other plugs. It is he 5th column over and 3rd row from the top (top being toward the engine. This is supposed too receive power from the ignition switch. I traced the pink wire from E3 to the evap vent solenoid. So, what wire is supposed to be in E3 and where does the pink wire supposed to go?
I was able to download a diagram of the 4 plugs with a chart saying what each wire is. This diagram does not fit my truck Can a correct table be found and made available? I don't know the original source of the diagrams I downloaded.
if the pcm is getting power from the 12 volt positive charge wire the engine will stay running with the key off because it being fed power from the alternator. it need an interuptable 12 positive wire from the key live only tih key on to pcm and dead when key is off thats why it stays running
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