LS1/4L60E swap in limp mode (p0758)
05-08-2012, 09:54 PM
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LS1/4L60E swap in limp mode (p0758) I finally finished the swap in my 67 Firebird. I swapped in a 2002 LS1 and 4L60E.
It started right up and runs great, except it starts off in 3rd gear, unless I downshift to 2nd. No 1st or 4th, even after I turn off the ignition or clear the code (p0758).
I have read and researched this, but I am getting conflicting information on how to troubleshoot this.
I would appreciate any advice you all could give me.
Does the fact that I never have 1st (even after key off and code cleared)
point to anything specific?
Is the pink power wire the only positive going into the trans?
The trans worked fine before the swap, but sat for about 6 months. I did nothing to it other than a fluid/filter change.
Thanks for any suggestions, I will be working on it tomorrow night.
Thanks, Charles
It started right up and runs great, except it starts off in 3rd gear, unless I downshift to 2nd. No 1st or 4th, even after I turn off the ignition or clear the code (p0758).
I have read and researched this, but I am getting conflicting information on how to troubleshoot this.
I would appreciate any advice you all could give me.
Does the fact that I never have 1st (even after key off and code cleared)
point to anything specific?
Is the pink power wire the only positive going into the trans?
The trans worked fine before the swap, but sat for about 6 months. I did nothing to it other than a fluid/filter change.
Thanks for any suggestions, I will be working on it tomorrow night.
Thanks, Charles
Last edited by 67fb-02z28; 05-09-2012 at 01:49 PM. Reason: punctuation issues
05-09-2012, 07:43 PM
#2
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Sorry that no one has answered you yet. The most common reasons are:
1. Connector not plugged into trans
2. Blown fuse
3. Wiring harness inside trans is defective.
4. One or more solenoids inside trans are defective.
5. Wrong/defective PCM. Is this the PCM that ran the trans before?
It is very unlikely there is anything mechanically wrong with the trans that would require removal. Most likely it is an electrical problem.
1. Connector not plugged into trans
2. Blown fuse
3. Wiring harness inside trans is defective.
4. One or more solenoids inside trans are defective.
5. Wrong/defective PCM. Is this the PCM that ran the trans before?
It is very unlikely there is anything mechanically wrong with the trans that would require removal. Most likely it is an electrical problem.
05-09-2012, 08:35 PM
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05-10-2012, 12:31 AM
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Thanks for the responses.
The code is p0758.
The connector is plugged in, but I can't remove/check it without removing the header to check for bent pins, dirt, etc.
It is getting 12 volts on the pink wire inside the trans, and at both solenoids. Both are at 22.5 ohms.
One has 12.5 volts with the ignition on, and < 1 on the ground side.
The other solenoid has 12.4, and 4.9 on the ground side.
Does that mean anything (4.9 on ground side)?
They both seem to work off the car with power and ground applied.
It is the same pcm as before. I sent it to Spare ECM to remove the VATS, as well as ther rear O2's and evap and a\c codes. They seem to have a good reputation. The harness is from Techrods.
I double-checked my brake switch (tcc), and park neutral switch as well.
Any ideas where I should look next? Thanks, Charles
The code is p0758.
The connector is plugged in, but I can't remove/check it without removing the header to check for bent pins, dirt, etc.
It is getting 12 volts on the pink wire inside the trans, and at both solenoids. Both are at 22.5 ohms.
One has 12.5 volts with the ignition on, and < 1 on the ground side.
The other solenoid has 12.4, and 4.9 on the ground side.
Does that mean anything (4.9 on ground side)?
They both seem to work off the car with power and ground applied.
It is the same pcm as before. I sent it to Spare ECM to remove the VATS, as well as ther rear O2's and evap and a\c codes. They seem to have a good reputation. The harness is from Techrods.
I double-checked my brake switch (tcc), and park neutral switch as well.
Any ideas where I should look next? Thanks, Charles
05-10-2012, 09:40 AM
#6
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The pink wire brings +12V to all the solenoids. The PCM then pulls the "other" side of the solenoid to ground to engage it.
The <1 Volt sounds like the PCM in engaging that solenoid.
The 4.9V on the ground side sounds like a problem - it should be 12V or <1 volt, but not in between. This indicates a wiring problem in the trans harness, a bad connection at the connector, a wiring error in the harness or a defective PCM. (I'll might be able to confirm that tonight, but with 40+ years of electronics experience, I'm pretty sure that is where your problem is.)
22 Ohms for those solenoids is correct.
Both solenoids must be engaged for 1st gear
The <1 Volt sounds like the PCM in engaging that solenoid.
The 4.9V on the ground side sounds like a problem - it should be 12V or <1 volt, but not in between. This indicates a wiring problem in the trans harness, a bad connection at the connector, a wiring error in the harness or a defective PCM. (I'll might be able to confirm that tonight, but with 40+ years of electronics experience, I'm pretty sure that is where your problem is.)
22 Ohms for those solenoids is correct.
Both solenoids must be engaged for 1st gear
05-10-2012, 07:52 PM
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Thanks. I thought 4.9 seemed strange, but didn"t have much info to base that on. Where would you suggest I start?
I can remove the header on the passenger side easy, and that should give me access to the connector.
From there maybe:
1- Check the connections \ pins?
2- Check continuity from connector to PCM?
3- Solenoid to connector?
Do you think I should focus first on the solenoid wire with the 4.9 volts?
Thanks for any advice you can offer.
I can remove the header on the passenger side easy, and that should give me access to the connector.
From there maybe:
1- Check the connections \ pins?
2- Check continuity from connector to PCM?
3- Solenoid to connector?
Do you think I should focus first on the solenoid wire with the 4.9 volts?
Thanks for any advice you can offer.
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05-12-2012, 08:52 PM
#9
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Thanks. I thought 4.9 seemed strange, but didn"t have much info to base that on. Where would you suggest I start?
I can remove the header on the passenger side easy, and that should give me access to the connector.
From there maybe:
1- Check the connections \ pins?
2- Check continuity from connector to PCM?
3- Solenoid to connector?
Do you think I should focus first on the solenoid wire with the 4.9 volts?
Thanks for any advice you can offer.
I can remove the header on the passenger side easy, and that should give me access to the connector.
From there maybe:
1- Check the connections \ pins?
2- Check continuity from connector to PCM?
3- Solenoid to connector?
Do you think I should focus first on the solenoid wire with the 4.9 volts?
Thanks for any advice you can offer.
I have no idea how easy your PCM connectors are to access. But if you can figure out how to measure things there, here is the "stock" info for a 2002 PCM:
1-2 Shift solenoid is Light-Green wire on pin 48 of Red connector.
2-3 Shift solenoid is Yellow/Black wire on pin 47 of Red connector.
It is probably the same color all the way to the trans connector (but not sure). I would try to measure the voltage somewhere along the way on those wires.
I was just thinking at 4.7V at the Solenoid could also mean it has a near-short and the PCM cannot pull it down to 0.1V. You could swap the solenoids for a quick check - watch out one is spring loaded.
If you can access the connector and pins with a mirror and light; checking for straight pins an no corrosion is a starting point.
05-13-2012, 09:07 PM
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Maybe I'm doing this wrong.
I took out the PCM, and tested for continuity from 47 on the red connector to the terminal on the connector (solenoid removed). I could not remember which was the ground side of the connector, so I tested both sides of 2-3 solenoid connector to 47 red.
No continuity on either side of connector.
Tried the 1-2 solenoid connector - No continuity.
My friend was touching the PCM contacts while I touched the solenoid connectors. We tested 46 also, and no continuity on either connector.
He accidentally tested 48, and it showed continuity to both connectors (one side of each). This is the malfunction indicator light wire.
I am lost. Does this make sense to you?
Thanks
I took out the PCM, and tested for continuity from 47 on the red connector to the terminal on the connector (solenoid removed). I could not remember which was the ground side of the connector, so I tested both sides of 2-3 solenoid connector to 47 red.
No continuity on either side of connector.
Tried the 1-2 solenoid connector - No continuity.
My friend was touching the PCM contacts while I touched the solenoid connectors. We tested 46 also, and no continuity on either connector.
He accidentally tested 48, and it showed continuity to both connectors (one side of each). This is the malfunction indicator light wire.
I am lost. Does this make sense to you?
Thanks
05-14-2012, 12:37 AM
#11
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Hmm, my doco says that #46 on the Red connector is the MIL light with a Brown/White wire. According to my doco, by pin numbers are correct for:
99-2002 Camaro, 97-2005 Corvette, 99-2003 Trucks.
Its easy to miscount.
But, you have the right idea, check for continuity with a helper. I would disconnect the battery, just to make sure there is no juice on any of these wires.
99-2002 Camaro, 97-2005 Corvette, 99-2003 Trucks.
Its easy to miscount.
But, you have the right idea, check for continuity with a helper. I would disconnect the battery, just to make sure there is no juice on any of these wires.
05-14-2012, 01:39 AM
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There are only 3 active pins on that part of the connector, 46-48. I saw this on several other schematics as well, so I think your info is correct.
If 47 had no continuity, then I would say replace the wire. What I don't understand is 48 with no continuity to the 1-2 solenoid connector. Shouldn't I have another DTC code? Also, why when we tested 46(MIL) did I have continuity on one side of each connector? Would a malfunction indicator light wired incorrectly set off p0758?
Before testing these wires I was sure the wire from 47 was bad, or the PCM was bad. A local tuner gave me a printout from alldata that pretty much outlined the steps I took so far. Now I don't know what to think.
Thanks,
Charles
If 47 had no continuity, then I would say replace the wire. What I don't understand is 48 with no continuity to the 1-2 solenoid connector. Shouldn't I have another DTC code? Also, why when we tested 46(MIL) did I have continuity on one side of each connector? Would a malfunction indicator light wired incorrectly set off p0758?
Before testing these wires I was sure the wire from 47 was bad, or the PCM was bad. A local tuner gave me a printout from alldata that pretty much outlined the steps I took so far. Now I don't know what to think.
Thanks,
Charles
05-14-2012, 08:45 AM
#13
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Sorry, but I don't know how to help you long distance without seeing and measuring things myself. I currently have a '98 PCM on my car and that has a completely different connector layout; else I would try to measure things in parallel with you.
This would help:
Tell us the colors of the wires on Pins 46-48.
And the colors of the wires at the trans connector.
Most aftermarket harnesses try to follow GM's color as much as possible.
This would help:
Tell us the colors of the wires on Pins 46-48.
And the colors of the wires at the trans connector.
Most aftermarket harnesses try to follow GM's color as much as possible.
05-14-2012, 10:15 PM
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Finally some good news. I retested #47 and 48 tonight without my friends "help".
From the PCM connector to the solenoid connector #47 does not have continuity.
# 48 does. I guess he wasn't making good contact with the probe.
This makes sense, 47 can not ground the solenoid.
Now I just need to find out if it's the wire or connector.
From the PCM connector to the solenoid connector #47 does not have continuity.
# 48 does. I guess he wasn't making good contact with the probe.
This makes sense, 47 can not ground the solenoid.
Now I just need to find out if it's the wire or connector.
05-15-2012, 07:44 AM
#15
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Glad to hear you are making progress.
Next, check continuity from the PCM connector to the trans connector on the harness. Here is a detailed pinout and schematic on the in-trans harness:
http://www.msgpio.com/manuals/mshift/wiring.html
(msgpio.com is the "open source" project for people are building their own trans controllers using a general purpose computer board, electronic parts and open source software.)
Next, check continuity from the PCM connector to the trans connector on the harness. Here is a detailed pinout and schematic on the in-trans harness:
http://www.msgpio.com/manuals/mshift/wiring.html
(msgpio.com is the "open source" project for people are building their own trans controllers using a general purpose computer board, electronic parts and open source software.)
Last edited by mrvedit; 05-15-2012 at 07:52 AM.
05-15-2012, 10:04 PM
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That is a lot of good info, thanks.
I think I figured this out last night.
My harness has two yellow and black wires from PCM to trans connector.
#47 red to pin B, and #51 red to pin L.
These 2 wires are reversed on my harness.
I am going to switch the wires at the PCM connector, and test the other wires as well since I'm there.
Hopefully this is the only issue.
Thanks again for the help, and I'll let you know how it works out.
I think I figured this out last night.
My harness has two yellow and black wires from PCM to trans connector.
#47 red to pin B, and #51 red to pin L.
These 2 wires are reversed on my harness.
I am going to switch the wires at the PCM connector, and test the other wires as well since I'm there.
Hopefully this is the only issue.
Thanks again for the help, and I'll let you know how it works out.
05-18-2022, 08:42 AM
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That is a lot of good info, thanks.
I think I figured this out last night.
My harness has two yellow and black wires from PCM to trans connector.
#47 red to pin B, and #51 red to pin L.
These 2 wires are reversed on my harness.
I am going to switch the wires at the PCM connector, and test the other wires as well since I'm there.
Hopefully this is the only issue.
Thanks again for the help, and I'll let you know how it works out.
I think I figured this out last night.
My harness has two yellow and black wires from PCM to trans connector.
#47 red to pin B, and #51 red to pin L.
These 2 wires are reversed on my harness.
I am going to switch the wires at the PCM connector, and test the other wires as well since I'm there.
Hopefully this is the only issue.
Thanks again for the help, and I'll let you know how it works out.
