HELP PLEASE ON CODE 1518

[BIGHEAVY]

Just used my proflash to chk a code and it was 1518 throttle actuator control module serial data circuit, do i need to take it in for service or is this nothing to worry about, the truck runs great especially after installing the proflash. any help is highly appreciated.
thanks
marc

[BIGHEAVY]

Just used my proflash to chk a code and it was 1518 throttle actuator control module serial data circuit, do i need to take it in for service or is this nothing to worry about, the truck runs great especially after installing the proflash. any help is highly appreciated.
thanks
marc

[Hummer Man]

Reset it and forget it unless its rough at idle or after the engine is hot. Recheck code in one week.

[HMSH2]

P1518
Notes

CIRCUIT DESCRIPTION
The Throttle Actuator Control (TAC) module and the Powertrain Control Module (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 test 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 diagnostic trouble set (DTC) sets.

CONDITIONS FOR RUNNING THE DTC


The ignition 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 control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands one of the following Reduced Engine Power modes:
The APP indicated angle is limited to a predetermined value to limit the amount of throttle control.
OR



The APP indicated angle is limited to 0 percent . The control module only allows the engine to idle.
OR



Under certain conditions the control module commands the engine OFF.
The message center displays Reduced Engine Power.
CONDITIONS FOR CLEARING THE MIL/DTC


The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Use a scan tool in order to clear the MIL and the DTC.
DIAGNOSTIC AIDS








The 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.
The 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.
The 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 is turned OFF. When the ignition is turned ON, the TAC module is powered-up before the PCM. The 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.
For an intermittent condition, Refer to Intermittent Conditions. See: Symptoms\Intermittent Conditions
TEST DESCRIPTION

Steps 1-8





Steps 9-18





Steps 19-29





The numbers below refer to the step numbers on the diagnostic table.


This step determines if the IGN relay is supplying a voltage to the THROT CONT fuse.
Increasing the engine speed to 3,000 RPM aids in locating a shorted throttle actuator motor control circuit. Depending on the polarity of the throttle actuator motor transistors, this DTC may not set with a fault in the control circuits. The throttle actuator motor is a bi-directional DC motor. Raising the engine speed changes the polarity of the transistors in the throttle actuator motor. This occurs because 1 set of the transistors are low (0 volts) and the other set are high (B+). Therefore, if 1 set of transistors are at a low voltage and the corresponding circuit is shorted low, DTC P1518 will not set. When the polarity of the transistors change this DTC sets. If this DTC does not fail this ignition, continue to monitor this DTC status while moving related harnesses and connectors.
Locating and repairing an individual condition may correct more than 1 DTC.

Hood Motorsports

- 1967 427 L71 Corvette (99%+ Bloomington Gold Certified, restored to original)
- 1998 Lingenfelter 383 C5 (over 500hp and 11's in the 1/4 mile)
- 2001 GMC Yukon Denali (22" wheels and tires, extensive multimedia system, and performance mods)
- 2002 Cadillac Escalade (Wife's/Mom's ride)
- 2003 H2 (Breathless Performance Stage 2B Package)

[HMSH2]

Big Heavy - if you give me your e-mail address, I can e-mail you a Word document that shows what I pasted above in more detail with diagrams and pictures. For some reason, the message board will not accept anything besides text.

Hood Motorsports

- 1967 427 L71 Corvette (99%+ Bloomington Gold Certified, restored to original)
- 1998 Lingenfelter 383 C5 (over 500hp and 11's in the 1/4 mile)
- 2001 GMC Yukon Denali (22" wheels and tires, extensive multimedia system, and performance mods)
- 2002 Cadillac Escalade (Wife's/Mom's ride)
- 2003 H2 (Breathless Performance Stage 2B Package)

[BIGHEAVY]

THANKS SO MUCH! but after all that i think i will take it in and let them deal with it and today after installing proflash yesterday chk engine on again this time it was 0449 so i am returning to stock and taking in. but thanks for taking the time to post all that info it is truly appreciated

[HMSH2]

Alright... any time anyone needs help with this type of stuff, I can look it up in a matter of seconds. Here is what I came up with for P0449.

P0449
Notes

CIRCUIT DESCRIPTION
An ignition voltage is supplied directly to the EVAP canister vent valve. The Powertrain Control Module (PCM) controls the EVAP vent valve by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. The PCM monitors the status of the driver. If the PCM detects an incorrect voltage for the commanded state of the driver, DTC P0449 sets

CONDITIONS FOR RUNNING THE DTC


The engine speed is more than 400 RPM .
The system voltage is between 6-18 volts .
CONDITIONS FOR SETTING THE DTC


The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
The above conditions are present for a minimum of 5 seconds .
ACTION TAKEN WHEN THE DTC SETS


The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC


The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Use a scan tool in order to clear the MIL and the DTC.
TEST DESCRIPTION

Steps 1-3





Steps 4-15





The numbers below refer to the step numbers on the diagnostic table.


Listen for a click when the valve operates. Be sure that both the ON and the OFF states are commanded. Repeat the commands as necessary.
This step verifies that the PCM is providing ground to the EVAP vent valve.
This step tests if the EVAP vent valve control circuit is grounded.

Hood Motorsports

- 1967 427 L71 Corvette (99%+ Bloomington Gold Certified, restored to original)
- 1998 Lingenfelter 383 C5 (over 500hp and 11's in the 1/4 mile)
- 2001 GMC Yukon Denali (22" wheels and tires, extensive multimedia system, and performance mods)
- 2002 Cadillac Escalade (Wife's/Mom's ride)
- 2003 H2 (Breathless Performance Stage 2B Package)