The Mountain Kat

Gotta love this stream of problems...
Yeah right. LOL

So I had my idler bearing die which caused the entire pulley to be eaten which caused the serpentine belt to shred one side.

New pulley and new belt. Now I am throwing the P1518 code.
Reduced Engine Power. Completely Reduced Engine Power. She won't start. Period. The code won't clear.
So I broke out the Dremel and a nice stainless steel wire wheel and cleaned the four grounds, all the connectors, and the ignition switch contacts.
Shiny bright.
Everywhere.
I looked for and could not find anywhere that the shredded belt might have torn up a wire.
She started and ran. Drove her around for two days. Went to drive her again and the P1518 is back.
(Does the on-board diagnostics show a P0606 if there is one or do I need to hook up my scanner? Seems to me that that code would be shown on-board.)
Looked up the code on here and in my service manuals. Tested the fuses, power, and continuity. Battery is at 12.4V and connections are shiny bright.
It would seem that it _could_ be a bad wire that I just happened to jiggle just right that allowed the car to run for a couple of days.
I have ~12V on both leads for the throttle actuator motor and 0Ω. The fuse has power when it is supposed to have power. If there is a short in the TAC ignition feed, or serial data feed, or throttle actuator feed, (etc. etc, ad infinitum) circuit where would the wires run so that I know where to look? Chasing wires through all of these corrugated lines can drive one to distraction...

The Mountain Kat

I pulled the TAC module and it looks as though someone has been into it before. Several of the retaining clips were broken off and it seems to have been sealed with hot glue. No getting it open without irreparable damage.
I'm going to go out and man handle the wiring here and there to see if the code will clear at some point. This might give me an indication as to where to rip open the loom and look for a wiring problem.

dadaroo

Here is a link to ponder on. Post 2 is interesting.

https://www.corvetteforum.com/forums...ealership.html

The Mountain Kat

Thanks for the answer. I'd read that one and most every post dealing with the P1518 code. Maybe it is nothing more than mere coincidence that this problem popped up after the belt/idler shred problem.
From my service manual it *appears* that there are only six wires of interest. I'll concentrate upon those today.
Good thing I like to fiddle with my car all the time or I'd put a .50 in her brain and part her out...
Kiddin', jest kiddin'...

dadaroo

Based on what you said I would not overlook the TAC itself and maybe a loose internal pin connection.

martysauto

Take a look at this

The TAC Module and the PCM communicate via a dedicated serial data circuit. This serial data circuit is separate from any other serial data circuit on the vehicle. Accurate transmitting and receiving of serial data requires not only good circuit integrity but also adequate system voltage. This diagnostic monitors the accuracy of the serial data transmitted between the TAC Module and the PCM. If the PCM detects a loss of data or invalid data, this DTC sets.

CONDITIONS FOR RUNNING THE DTC
The ignition switch is in the crank or run position.
The ignition voltage is greater than 5.23 volts .
CONDITIONS FOR SETTING THE DTC
Invalid or missing serial data messages are detected for a predetermined amount of time.
All of the above conditions met for less than 1 second .
ACTION TAKEN WHEN THE DTC SETS
The PCM will illuminate the Malfunction Indicator Lamp (MIL) when this diagnostic runs and fails.
The Reduced Engine Power message displays on the drivers information center.
The PCM records the operating conditions at the time during which the diagnostic fails. The PCM stores this information in the Freeze Frame and/or Failure Records.
If no other TAC System DTCs are set, the TAC System will operate in Reduced Engine Power mode. If certain TAC System DTCs are set at the same time, the TAC System either defaults to a more tightly restricted mode of operation if the TAC determines that limited safe operation is possible, or the TAC commands the engine to shut down.
If DTC P0606 is set with DTC P1518, the TAC commands an engine shut down.
CONDITIONS FOR CLEARING THE MIL/DTC
The PCM turns OFF the MIL after three consecutive drive trips during which the diagnostic runs and does not fail.
A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.
A History DTC clears after forty consecutive warm-up cycles if this or any other emission related diagnostic does not report any failures.
Clear the MIL/DTC information with a scan tool.



DIAGNOSTIC AIDS

IMPORTANT:
Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect the PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM/TAC modules.
For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616-A. Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Diagrams.
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 TAG 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 TAG Module/PCM serial data circuits for intermittent connections.
Inspect the TAC module connectors for signs of water intrusion. When this occurs, multiple DTCs should be set and no circuit or component problems can be located.
When the TAC module detects a problem within the TAG System, more than one TAC System related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual problem may correct more than one DTC. Keep this in mind when reviewing captured DTC info.
For an intermittent condition, refer to Symptoms. See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Symptom Related Diagnostic Procedures

The Mountain Kat

Jeezz...

So far I have found that the 13 month old battery wouldn't keep a full charge. Good power at the Throtcont fuse. I swapped it out with a good battery. I turned the ignition on and went to the fusebox. No current at the ThrotCon fuse. WTH?!?
My son came out and heard the alarm sounding in the car so he turned off the key.
Oops.
Kinda...
I had him turn the key back on and I noticed no click from the IGN relay. I checked the fuses that it should energize. Zip. Nada.
I replaced the IGN relay and now the the ThrotCon fuse is active. The P1518 code also went away.
Cool.
For a minute anyways.
Now I have a U1040HC, P1571HC, P1689HC, and a TCS "No Comm".
I reach down to check the EBCM and find that the latch is missing. Missing and not just dislodged. The large flat end of the front hold-down pin is broken off.
Great.
Safety wiring seems to be in order to retain the connector.

The Mountain Kat

I've run through the diagnostics routine. No shorted serial data link wires. I reconnected the cables to the PCM, the TAC, and the EBTCM. The red connector seemed a little too difficult to get on correctly. Not that it was hard to do but it wasn't as easy as the blue connector.
Strangely enough the TCS code that has been popping up for the past couple of years seems to have gone off as well.
All that I have done to change the problem was to remove and reinstall the connectors on the modules.

Now there are no codes showing *but* I haven't driven anywhere.
I'll take her out for a spin this weekend and see what happens.