Team Chevelle banner

68 chevelle sedan II

3K views 18 replies 4 participants last post by  NReilly 
#1 ·
Hey everyone, just a little update on the Chevelle. Tried to bump my old thread but it was apparently too old.


Anyway I got myself a L18 BBC Gen 7. And sold my 396 and my 454.

In the process of getting it all fitted up with the 4L80e. Amazingly the giant oil pan just barely cleared the cross member. Might have to do a little trimming though as the steering arms hit the bottom as I do a full right turn.


Also, my power steering seems to be hitting my steering box, so I will have to find a way to remedy that problem. I did figure out most out my wires though!
 

Attachments

See less See more
5
#3 ·
Looks worse then it is. I actually have all my wires figured out, just need to clean it up and see if i can mount the PCM inside. Throttle goes right to a controller like a LS engine. Everything else going to the interior is the OBD2,3 wires for ignition,brake switch for the TQ converter, speedometer, TAC, and I will probably take advantage of the cruise control functions as you do not need any separate modules as it is electronic throttle body.
Then from the fuse box i got a couple wires for primary and secondary fuel pump if I want. Everything else is plug and play. PCM controls the throttle box and connects and runs the transmission. I just need to run 2 wires from the fuse box to a 12v ign wire to power the transmission shift solenoids. As they used to get power from a module in the interior of the donor truck.
 
#4 ·
As for the body, I have new rockers inner and outters, 1/4 panel skins, and trunk drop downs I am going to be putting in once I get the engine mostly sorted. I really slapped this thing together when I was younger, so I have a lot of stuff to fix. Also still have plans to make either kevlar or carbon fiber fender liners. I Also need to cut these 1/4 skins for a 2 door, as I can not get 4 door ones, so it will have to be under the line that only 2 doors have. But on the plus side, I will have perfectly shaped metal extra to patch the doors with.
 

Attachments

#5 ·
Haven't Been on it too much, mostly from school taking up a lot of energy. And I don't have any room in the garage to do what I need to.
But the wiring is sorted, just need to plug it all in. Undid the whole engine harness to angle it towards the firewall instead of the drivers front, since I want the PCM and such inside the car.
Engines oil pan is now clearing the cross member, just have to figure out how to clean the steering arm.

Now that the engine is sitting how I want I can bolt up the transmission and see if it clears the trans tunnel. Then I can see how much my driveshaft needs to be shortened.
 

Attachments

#6 ·
Made a bit of progress with the car. Found another L18 at the local pick n pull, grabbed the oil pan and the intake to have spares for modifications haha.
Took the pan into work and cut and welded it. It now clears the steering arms by about 3-4 mm at full tilt. Also not sure why they made the pan square on one side and smooth on the other. I can only think of wind-age being why.
 

Attachments

#7 ·
So I finally have the garage to myself, and can start working on this again! Got most of the wiring sorted, fuel pump is in, new sending unit with a return is in. I mostly just want to get everything wired in and make sure it is happy when it starts up so I can finalize how I am going to have everything sitting.
 

Attachments

#8 ·
Chopped the ends off of the stock manifolds just to get them to barely clear the frame. And Since I don't have headers yet that will fit being that it is a tall deck.

Got the wires on and made a couple of grounding points, Got the battery hooked up. Wouldn't turn the engine on with PCM, bypassed it, would turn and have fuel but no spark or ignition. Checked the back of the engine harness and found a little ground I forgot to ground right beside the Crank position sensor.

Fired up right away but died right away, spent about 10 minutes checking things and trying again, would still just start up and die. Sometimes with a backfire.
Ended up plugging in my OB2 scanner and got code 1125. Checked into it a little more and I think I found my problem. I had wired up a 2006+ DBW pedal to a 2004 TAC module. Apparently that is a no no even though all the wires are the same color.

Also made a little bracket for the pedal to mount to the floor.

Guess I am going to run to Pick N Pull this weekend to get a newer TAC module.
 

Attachments

#9 ·
Well, grabbed a whole matching pedal assembly from an 06 Avalanche. TAC/wire/pedal. Fixed the p1125 code error, but now I am getting p1518 at part throttle. The pedal works if I mash it to WOT and off again, but once I go slowly or mash it part way it will throw the p1518(TAC to PCM communication) and totally kill the throttle all together. Which I believe in turn kills the engine, since I am still not getting it to run. Longest I got it to run for was about 4 seconds.

Got quite frustrated, and wanted to make sure it was nothing I wired in wrong. So I took out the harness again and did more trimming and completely got rid of the OEM truck fusebox. Looks way better and got more length out of some of my wires that I really needed. And a lot more on some that I didn't haha. But after all of that I am still having the same issue with it starting and dying and throwing p1518 codes. I believe it is either the throttle body itself or the pedal being to new for the PCM to recognize.
 

Attachments

#11 ·
For some reason that page wont load for me. Or at least at this time. Maybe the website is down ATM.

Went to the wreckers and I grabbed another TB and the harness from the TB all the way to the TAC from a 2006 to match the pedal and TAC, tried just the TB with same result. Re pinned the newer TB harness it into the old TAC plug. And it seemed to be working properly. Wouldn't throw the code at part throttle, seemed to have full range of pedal.

Started it up, ran for about 4 seconds and died. Tried again a few times and would just keep dying after 2 seconds. Then finally it started throwing the code again. And once again anything partial or slow pedal would throw the code and kill it. Really tempted to convert to cable. Cause this is just stupid.

I noticed my original TB had a 2.5 mm hole in the back of the casting going into the electronics area. Which I am sure was not helping the situation. But there was no difference between the 03 TB and the 06 TB, even the harness was the same wire pinout. And same wires to the cruise control and PCM.
 
#13 ·
Worked for me......

P1518 CHEVROLET - Electronic Throttle Module to PCM Communication

Condition/Concern:
Customers may have a concern of lack of power and engine light on. DTCs set will almost always contain a P1518 and may contain any of the following (P1516, P2108, P0220, P0120, U0107). An improperly torqued TAC module ground may be at fault. The Ground is listed as G104 on TAC module schematic which is incorrectly labeled on SI document ID 855376. The correct ground is G103. The locator for SI states that G103 is located on the left hand side which is incorrect. However, there have been field reports stating that G104 has also corrected this condition. G104 is a horizontal bolt in the rear of the left head and extremely difficult to reach. G104 should also be tightened at the same time.

There have also been field cases where ground G110 on the outer drivers side frame rail caused a P1518 code and an intermittent connection at splice 102 on the intake.

All published SI diagnostics should be followed in addition to following the recommendation listed.
Recommendation/Instructions:

Tighten ground G103 located behind the right cylinder head (passenger side) just below the head and mounted into the block. The ground uses a 13 mm bolt head mounted vertically to the engine block just above the bell housing.

• DTC P1518 sets if the battery voltage is low. If the customer's concern is slow cranking or no crank because battery voltage is low, ignore DTC P1518. Clear any DTCs from memory that may have set from the low battery voltage condition.
• DTC P1518 sets when there is a short to B+ on the TAC module ground circuit. Inspect the fuses for the circuits that are in the TAC module harness--i.e. cruise, brake. An inspection of the fuses may lead you to the circuit that is shorted to the TAC module ground circuit.
• DTC P1518 sets if the TAC module ignition feed circuit is shorted to a B+ supply circuit. The TAC module stays powered-up when the ignition switch is turned OFF. When the ignition switch is turned ON, the TAC module is powered-up before the PCM. DTC P1518 sets because no communication is detected by the TAC module from the PCM. Inspect related circuits for being shorted to a B+ supply circuit.
• Inspect the TAC module power and ground circuits and the TAC module/PCM serial data circuits for intermittent connections.
• Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
• When the TAC module detects a problem within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than 1 DTC. Remember this if you review the stored information in Capture Info.


Conditions for Setting the DTC
• The TAC module detects that the predicted and the actual throttle positions are not within a calibrated range of each other.
• The PCM and the TAC cannot determine the throttle position.
• Both of the TP sensors are invalid.
• All of the above conditions are met for more than 1 second.



Condition/Concern:
A vehicle may be brought into the dealer for a reduced power message, and DTCs P0120, P0220, P1516, P2101, or P2135.

The Throttle Actuator Control (TAC) / throttle body type trouble codes, may be caused by a loose wiring crimp at the throttle body connector, or a broken throttle body circuit.

Recommendation/Instructions:
Complete the current SI diagnostics for any symptoms or trouble codes found. If a intermittent T/P or TAC module type code is occurring complete the inspections below.

Inspect all related throttle body terminals for a loose wiring crimp. The loose crimp may be difficult to find, and the poor connection will be between the terminal and the copper strands of the wire. Wiggle test the individual throttle body circuits to see if the concern can be duplicated.
Inspect the related circuits for broken wires inside the insulation. The outer wire insulation may look fine, but the internal copper strands may be partially broken. Breaks in the wires usually occur within 1 to 4 inches of the throttle body connector. Wiggle testing may also induce a trouble code to set.
On C/K trucks complete SI procedures for voltage drop on grounds G103 and G104. Grounds G103 or G104 may be loose or corroded.

If a terminal crimp or a broken wire has been found, repair or replace only the circuits involved.

Keep us updated.
 
#14 ·
Worked for me......

P1518 CHEVROLET - Electronic Throttle Module to PCM Communication

Keep us updated.
Thanks Bill! I actually took the ground for the TAC out of the G103, and put on to a separate ground under the dash when I deleted the Truck fusebox.
I am starting to think maybe the TAC is just sending slightly off information to the PCM.


This site was quite helpful with some testing of the pedal and throttle bodies. As it gives voltage sweeps and min-max's

https://www.lsenginediy.com/gm-gen-iii-ls-pcmecm-electronic-throttle-equipment-guide/

But I haven't played with it much the last few days. But to keep moving forward a bit. I decided to throw the transmission in, my god are 4L80Es heavy! I thought they were 200-250lbs. but apparently they are 250lbs, and another 60lbs with the torque converter. Don't recommend installing one by yourself haha. Still need to get a X-member mount, but at least I can figure out how much I have to shorten my driveshaft.
 

Attachments

#15 ·
So, I am not sure how the throttle got fixed, maybe it needed to actually run first. But I found out that the VATS system was killing my engine.

Ended up putting my PCM into my dads 2003 6.0 2500hd truck, relearned his key to my PCM, got the truck to run. Pulled the BCM while it was running, made sure it started again with it off. Stuck it back into my car and it magically started and ran!



Also got a heater installed into the garage this fall, right before the snow really started to fly. Which means I should be working on this while I am in school for January and Febuary.
 
#16 ·
Finally made a bit of progress on this thing. Got the pedal mounted and custom made a truck one to fit.
Also found out that the power steering pump decided to fit. And kind of rigged it to fit with the old hoses.
 

Attachments

#17 ·
Did some more work on it this weekend. Was hoping to get my driveshaft back Friday but I suppose it will be done tomorrow, which is fine.

But I finally got me a chop saw, so I could do my headers and cut my crossmember.

She is all bolted on now, just need to finish a few things.
 

Attachments

#18 ·
Thought I posted more pictures, but I suppose I missed some! Got a lot of it back together. Took it for a drive around the block as well! Put it away for the winter so other people could park in the garage. Going to take time off work this June to work it it and hopefully get it all welded up and in primer!
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top