Hi all , new to the site , 07 trailblazer , truck starts and immediately goes in limp home mode , numerous codes set . I have no pwr. to fuse #23 ETC . checked fuse box for open circuit , good I m trying to find where pwr. comes from for this circuit . If i power up load side of fuse truck runs normal . Don
SOLVED! fuse #23
- Thread starter Don Bucko
- Start date
Fuse 23 appears to be powered by the powertrain relay #57.
Power Distribution Diagram 16 — 2007 Chevy Truck TrailBlazer 4WD L6-4.2L Service Manual | Operation CHARM
Detailed repair manual for the 2007 Chevy Truck TrailBlazer 4WD L6-4.2L.
charm.li
Mooseman
Moderator
Investigating any LIMP MODE Issues follows an organized Diagnostic Methodology:
Ivan, "The Man From PHAD" (Pine Hollow Diagnostics) along with Keith DeFazio from New Level Auto Diagnostics on Staten Island, NY in the Dead of Winter investigate a Weird Limp Mode issue with a Trailblazer that follows the direction set by @Mooseman and a Troubled Five Volt Reference Signal coming from the Electro-Viscous Fan. THIS is a fascinating exploration of this Diagnostic and Repair:
This Video is very instructive in a General Sense to provide an Overview of Limp Mode Conditions and How to Diagnose Limp Mode Issues:
Ivan, "The Man From PHAD" (Pine Hollow Diagnostics) along with Keith DeFazio from New Level Auto Diagnostics on Staten Island, NY in the Dead of Winter investigate a Weird Limp Mode issue with a Trailblazer that follows the direction set by @Mooseman and a Troubled Five Volt Reference Signal coming from the Electro-Viscous Fan. THIS is a fascinating exploration of this Diagnostic and Repair:
This Video is very instructive in a General Sense to provide an Overview of Limp Mode Conditions and How to Diagnose Limp Mode Issues:
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It powers the MAF/IAT and provides an IGN 1 signal voltage back to the PCM at Connector 1, pin 13.
(1) Dirty MAF and Clogged Air Filter.
(2) Bad or Shorted MAF/IAT Plastic Connector.
(3) Bad or Shorted MAF/IAT Harnessing.
(4) Possible signs of NA Deer Mice in Residence (Chewing-Gnawing Wiring).
(5) Follow CDC Precautions for *** HANTA Virus Infection via Inhaling Mouse Dust.
(6) Use an N-95 Face Mask, OSHA Eye Protection and Mil11 Nitrile Gloves @ Work.
(7) Discourage Mice Infestation using Packets Soaked in Peppermint Oil under Hood.
*** Beware seeing Mouse Nesting, Feces and Urine accumulation inside and around Engine Bay as contracting this Illness Kills around 40% of those Infected..
Jimmy from "1Road" works on a Problem with his GM-GMC Vehicle(s) and in THIS case... The Question Begs, "Does CRC MAF Sensor Solvent Spray REALLY Work?"
(2) Bad or Shorted MAF/IAT Plastic Connector.
(3) Bad or Shorted MAF/IAT Harnessing.
(4) Possible signs of NA Deer Mice in Residence (Chewing-Gnawing Wiring).
(5) Follow CDC Precautions for *** HANTA Virus Infection via Inhaling Mouse Dust.
(6) Use an N-95 Face Mask, OSHA Eye Protection and Mil11 Nitrile Gloves @ Work.
(7) Discourage Mice Infestation using Packets Soaked in Peppermint Oil under Hood.
*** Beware seeing Mouse Nesting, Feces and Urine accumulation inside and around Engine Bay as contracting this Illness Kills around 40% of those Infected..
Jimmy from "1Road" works on a Problem with his GM-GMC Vehicle(s) and in THIS case... The Question Begs, "Does CRC MAF Sensor Solvent Spray REALLY Work?"
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Hi TJ , relay #57 is not turning on . I have 12v. on both terminals key on or off and if I jumper a ground to it energizes . I m having trouble finding what turns it on . Don
The PCM provides the ground to activate the Powertrain relay #57. Right this moment I cannot say what causes the PCM to activate relay #57. It could be one of the several wires from the ignition switch to the PCM or it may be a power-moding message from the BCM.
Fuse #23 (ETC) supplies +12VDC (Hot on RUN) directly to the PCM connector C3 on Pin #17. It is called IGN 1 Voltage. Possible Problems include:
(1) A Wiring Problem.
From Rodents Chewing on Things. Look things over REAL CLOSE with a Very Bright Flashlight.
(2) A Bad Fuse Panel.
Try Unbolting the Four Galvanized Studs and Spraying the Under Blocks and the Copper Tracing and Fuse inserts with CRC Electrical Solvent Spray. Let everything Dry Out and then Snug it all back together and Try Starting the SUV.
(3) A Bad PCM.
...or a Poorly Attached C3 Connector. Try Removing the C3 - to - PCM Connector and Spraying it out with CRC Electrical Solvent... then let it Dry Out and Re-attach it in place. Actually... it would NOT Hurt to R&R C1 and C2 Connectors and do likewise to THEM as well.
See Post #4 in THIS Thread for the PCM (and BCM) Pinouts:
gmtnation.com
(1) A Wiring Problem.
From Rodents Chewing on Things. Look things over REAL CLOSE with a Very Bright Flashlight.
(2) A Bad Fuse Panel.
Try Unbolting the Four Galvanized Studs and Spraying the Under Blocks and the Copper Tracing and Fuse inserts with CRC Electrical Solvent Spray. Let everything Dry Out and then Snug it all back together and Try Starting the SUV.
(3) A Bad PCM.
...or a Poorly Attached C3 Connector. Try Removing the C3 - to - PCM Connector and Spraying it out with CRC Electrical Solvent... then let it Dry Out and Re-attach it in place. Actually... it would NOT Hurt to R&R C1 and C2 Connectors and do likewise to THEM as well.
See Post #4 in THIS Thread for the PCM (and BCM) Pinouts:
BCM pinout
Looking to pick up on the reverse lamp circuit at the BCM. I've found sources that indicate it may be a light green wire, but there are several of them back there. One of which is a com wire that didn't take kindly to having a test light on it... anyone have a pinout for the connectors or a...
gmtnation.com
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A small correction:
This is a 2007 with a P12PCM. A P12 PCM has nothing connected to Connector 3, pin #17.
On a 2007 with a P12 PCM the powertrain relay provides a IGN 1 power to the PCM at Connectir 1, pin #13.
you need to see if the ground is coming out of the pcm on c1 pin 38. The easiest check would be to watch it at the relay (57). Another check would be an impedance check at the same point (without any battery hook up ... ie positive post disconnected). This check is just a "thumb check" to see if any kind of circuitry is connected to that wiring / pin. You can then do the same check again with battery connected back up and turning the key to run to see if any change in the impedance reading can be seen to indicate some circuit activity.
One more test: pull the connector at the pcm, locate the pin38. With the relay installed and key in run, check for voltage on the pcm cable (pin 38)... the 12v should be coming thru to that point if there is continuity all the way thru. IF that is the case, then it is likely you have some issue with the PCM not grounding that pin.
A picture of the dash lights might help show what you are seeing when you are in the "limp mode running".
One other thing... assuming you haven't been flashing your PCM for whatever reason, then the other place to look is under the front fuse box "layers" to check the tracks going to the relay (and coming from the PCM).
One more test: pull the connector at the pcm, locate the pin38. With the relay installed and key in run, check for voltage on the pcm cable (pin 38)... the 12v should be coming thru to that point if there is continuity all the way thru. IF that is the case, then it is likely you have some issue with the PCM not grounding that pin.
A picture of the dash lights might help show what you are seeing when you are in the "limp mode running".
One other thing... assuming you haven't been flashing your PCM for whatever reason, then the other place to look is under the front fuse box "layers" to check the tracks going to the relay (and coming from the PCM).
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problem turned out to be open on c38 wire , PCM to fuse panel . Thanks to everyone who helped out , greatly appreciate . Don
Just for the record, was the break found and was it inside the fuseblock or external?
BTW, many years ago I lived in Shrub Oak.
Hey TJ , working on it outside I didnT open the harness , always felt better seeing the actual break .Don
Congrats on solving the problem. Do you have any photos of the area that was causing the trouble?