P1516 DTC truck goes into limp mode.

[haulinit]

My friend called me and asked if I could take a look at his truck it keeps going into limp mode while driving. The truck is a 2003 with a 5.3L, the DTC that came up was P1516. I watched the TAC "throttle Acutation Control" functions, when the truck goes into limp mode it throws a fault for "State15 remote acutation". I'm thinking his problem is in the TB with the drive by wire controls, which after looking appears to be non servicable! Has anybody had any experience with this? I would feel really bad if he spent the money on a new TB and that did not fix it.

PS: We did the wiggle test, checked for broken wires, and the grounds.

Thanks
Shawn

[Boost]

1
Did you perform the Diagnostic System Check-Engine Controls?
Go to Step 2
Go to Diagnostic System Check - Engine Controls

2
Is DTC P1518 set?
Go to DTC P1518
Go to Step 3

3
Is DTC P2135 set?
Go to DTC P2135
Go to Step 4

4
Important: Low system voltage may cause this DTC to set. Clear DTCs if low system voltage has been experienced.

•Turn OFF the ignition for 15 seconds.
•Turn ON the ignition, with the engine OFF.
•Observe the throttle position (TP) sensor 1 and TP sensor 2 angle parameters with a scan tool.
•Slowly depress the accelerator pedal to wide open throttle (WOT) and slowly return it to the released position.
Does the scan tool indicate both angle parameters increasing as the pedal is depressed to WOT and decreasing as the pedal is released?
Go to Diagnostic Aids
Go to Step 5

5
•Turn OFF the ignition.
•Disconnect the throttle actuator motor harness connector.
•Remove the air inlet duct from the throttle body.
•Inspect the throttle body and throttle plate for the following conditions which may cause the throttle plate to bind:
• Debris--If debris is found, clean the throttle body and repair the source of contamination.

• Damage or evidence of tampering--If the throttle body and/or throttle plate is damaged, replace the throttle body. Refer to Throttle Body Assembly Replacement .

Did you find and correct the condition?
Go to Step 17
Go to Step 6

6
With your hand, slowly open the throttle plate to WOT and back to the closed position several times.

Does the throttle plate move smoothly without binding in both directions?
Go to Step 7
Go to Step 14

7
•Turn Off the ignition.
•Disconnect the throttle body harness connector.
•Connect the jumper wires between the TP sensor terminals of the throttle body harness connector and the corresponding TP sensor terminals of the throttle body.
•Turn ON the ignition, with the engine OFF.
•Open the throttle blade to WOT, then to the closed position by hand.
•Observe the TP sensor 1 and TP sensor 2 angle parameters with a scan tool.
Does the scan tool indicate both angle parameters increasing as the throttle plate is moved to WOT, and decreasing as the plate is moved to the closed position?
Go to Step 8
Go to Step 15

8
•Turn OFF the ignition.
•Disconnect the throttle actuator control (TAC) module harness connector containing the throttle actuator control motor circuits.
•Turn ON the ignition, with the engine OFF.
•Test the TAC motor circuits for a short to voltage with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 17
Go to Step 9

9
Test each TAC motor circuit for an open or high resistance with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 17
Go to Step 10

10
Test each TAC motor circuit for a short to ground with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 17
Go to Step 11

11
•Disconnect the other TAC module harness connector.
•Test for a short between each TAC motor circuit and all other TAC module circuits with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 17
Go to Step 12

12
•Turn OFF the ignition.
•Connect the TAC module.
•Connect a test lamp between the two TAC motor circuits at the TAC motor harness connector.
•Turn ON the ignition, with the engine OFF, and observe the test lamp.
Did the test lamp illuminate briefly when the ignition was turned ON?
Go to Step 13
Go to Step 15

13
Inspect for poor connections at the TAC motor harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?
Go to Step 17
Go to Step 14

14
Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .

Did you complete the replacement?
Go to Step 15
--

15
Inspect for poor connections at the TAC module harness connectors. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?
Go to Step 17
Go to Step 16

16
Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement .

Did you complete the replacement?
Go to Step 17
--

17
•Clear the DTCs with a scan tool.
•Turn OFF the ignition for 30 seconds.
•Start the engine.
•Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?
Go to Step 2
Go to Step 18

18
Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?
Go to Diagnostic Trouble Code (DTC) List
System OK