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Dan, Auto Technician
Category: Chevy
Satisfied Customers: 3490
Experience:  GM Mark of Excellence/ Service Guild Participant with 13 years experience, ASE Master Certified
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How to fix a 2003 Chevy Silverado P1516 (TAC module)

Customer Question

How to fix a 2003 Chevy Silverado P1516 (TAC module)?
Submitted: 8 years ago.
Category: Chevy
Expert:  Dan replied 8 years ago.
#PIP3089B: SES Light And Reduced Engine Power DTC P0120 P0220 P1516 P2135 - keywords accelerator actuator APP blade body connector connection DTC L33 L59 LH6 LR4 LM7 LS1 LS2 LQ4 LQ9 module position reduce sensor - (Oct 31, 2006)

Subject:SES Light and Reduced Engine Power DTC P0120 P0220 P1516 P2135

Models:2004-2006 Buick Rainer
2005-2006 Cadillac CTS-V
2003-2006 Cadillac Escalade
2003-2006 Chevrolet Avalanche, Corvette, Express, Monte Carlo, Silverado, SSR, Suburban, Tahoe, Trailblazer
2003-2006 GMC Envoy, Savana, Sierra, Yukon
2003-2006 Hummer H2
2005-2006 Pontiac GTO
Equipped with a 4.8 5.3 6.0 or 7.0 V-8 Engine


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.


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.


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.

  1. 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.
  2. 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.
  3. 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. There is a throttle body pigtail connector available through GMSPO, but installing this pigtail connector may cause other intermittent TAC module/TP codes at a later date. If this pigtail must be used, please follow the SI procedures for Splicing Copper Wire Using Splice Sleeves. (the proper Kent-Moore crimping tool must be used for this repair)

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Customer: replied 8 years ago.

I have been having problems with my check engine light. It has been coming on quite frequently and when it does come on, the truck goes into "reduced engine power." The code for the check engine is P1516. I have replaced the TAC Module with a used one. I have also replaced the wiring harness coming off the throttle body. I am wondering what part could be next to replace to solve the problem.

Expert:  Dan replied 8 years ago.
#03-06-04-032: Check Engine Light On with No Driveability Concerns, DTC P0120, P0220, P1516, P1518 (Clear Code) - (Jun 16, 2003)

Subject:Check Engine Light On with No Drivability Concerns, DTC P0120, P0220, P1516, or P1518 Set (Clear Code)

Models:2003 Cadillac Escalade, Escalade EXT, Escalade ESV
2003 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2003 GMC Sierra, Yukon, Yukon XL
with 4.8L, 5.3L or 6.0L Engine (VINs V, P, T, Z, N, U - RPOs LR4, LM4, LM7, L59, LQ9, LQ4,)



Some owners may comment that the Check Engine Light is illuminated and there is no driveability concern. Upon investigation, the technician may find codes P0120, P0220, P1516 or P1518. Also, technicians may note that low voltage codes P0562, P0563, P1637 or P1638 have been set.


The Tach module may set the code in error if it operates at a battery voltage of 4.5 to 5.0 volts.


If the vehicle has stored one of the low voltage codes, P0562, P0563, P1637 or P1638, follow the appropriate diagnostics for the low voltage code. In most cases, this will lead to correcting the concern without replacing any Electronic Throttle Control (ETC) components.

If codes P0120, P0220, P1516 or P1518 are present without any of the low voltage codes, the technician should observe the Engine RPM in the fault record.

If the Engine RPM in the fault record is zero and the customer indicates that the vehicles has experienced a low voltage condition, the code should be cleared and the low voltage should be diagnosed and corrected.
If the Engine RPM is zero and the customer indicates that there have been no low voltage conditions, then the P1516 diagnostic aids for intermittent concerns should be used to diagnose and correct the vehicle
If the Engine RPM is greater than zero, then check for an obvious loose ground at G103 located next to the right cylinder head just below the head and mounted into the block. Also, check G104 located behind the left cylinder head. Then verify all electrical connections at the TAC module.

If the concern is still not resolved, contact Technical Assistance.

#PIP3087A: Crank, No Start, Stall, Hard Start, and No Cranking RPM - kw nostart nocrank 4.3 4.8 5.3 6.0 8.1 ignition information injector L18 L59 LM7 LQ4 LQ9 LR4 LU3 PCM L33 - (Oct 13, 2004)

Subject:Crank No Start, Stall, Hard Start, and No Cranking RPM.



The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.


Crank no start, stalling, hard start, loss of cranking RPM, or loss of ignition 1 voltage. Depending on the model and the conditions present DTCS B3031, P0120, P0220, P0135, P0141, P0155, P0161, P1516, P1631, P2101 P2135, U1016 and U1064 may also be stored. It may also be noted that normal crank RPM registers momentarily as the key is released from the crank position.


If the "Engine Cranks but Does Not Run" SI diagnostics did not isolate a concern, the following information may help: Using the Tech 2, monitor the Ignition 1 voltage parameter when the customer concern is duplicated. With a fully charged battery, the Ignition 1 voltage parameter should not drop below 10 volts while cranking. If it does, measure the main voltage supply to the Underhood Bussed Electrical Center (UBEC) during the condition. If the UBEC voltage supply is above 10 volts but the Tech 2 Ignition 1 Voltage Parameter is below 10 volts, replace the Ignition 1 Relay.

Customer: replied 8 years ago.
How do you wire in a new wiring harness for the TAC module? What is that wiring harness part number?
Expert:  Dan replied 8 years ago.
You would need to visit your local GM parts dept. for the part pricing and availability. Also, be sure to check the grounds and integrity of the wiring before any parts are replaced.
Customer: replied 8 years ago.
The voltage is fine it read 5.23 volts. What else could it be?