Avalanche, Sierra, Silverado, C&K Series, 1999-2005

6.0L V8 VIN U Std 4

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Trouble Code: P1220



TP Sensor 2 Circuit Malfunction

Possible Causes:



TP2 sensor signal circuit is open, shorted to ground or to power
 
TP2 sensor VREF circuit is open, shorted to ground or shorted to system power (B+)
 
TP2 sensor ground circuit has a high resistance condition
 
TP2 sensor is damaged or has failed
 

Trouble Code: P1221



TP Sensor 2 Signal Correlation

Possible Causes:



TP2 sensor connector is contaminated, dirty or contains water
 
TP2 sensor signal, ground or VREF circuit has high resistance
 
TP2 sensor VREF circuit has a high resistance condition
 
TP2 sensor ground circuit has a high resistance condition
 
TP2 sensor is damaged or has failed
 
TAC controller or the throttle body is damaged or has failed
 
TSB 02-06-04-005 contains a repair procedure for this code
 

Trouble Code: P1275



Accelerator Pedal Position Sensor 1 Circuit Malfunction

Possible Causes:



APP1 sensor connector is contaminated, oily or contains water
 
APP1 sensor signal, ground or VREF circuit high resistance
 
APP1 sensor VREF circuit is open, shorted to ground or to B+
 
APP1 sensor signal or ground circuit has high resistance
 
APP1 sensor is damaged or has failed
 
TAC module is damaged or has failed
 

Trouble Code: P1276



Accelerator Pedal Position Sensor 1 Range/Performance

Possible Causes:



APP1 sensor connector is contaminated, oily or contains water
 
APP1 sensor signal circuit is open or shorted to ground
 
APP1 sensor signal circuit is shorted to VREF or system power
 
APP1 sensor ground circuit is open or has high resistance
 
APP1 sensor VREF circuit is open or shorted to ground
 
APP1 sensor is damaged or has failed
 

Trouble Code: P1280



Accelerator Pedal Position Sensor 2 Circuit Malfunction

Possible Causes:



APP2 sensor connector is contaminated, oily or contains water
 
APP2 sensor signal, ground or VREF circuit high resistance
 
APP2 sensor VREF circuit is open, shorted to ground or to B+
 
APP2 sensor signal or ground circuit has high resistance
 
APP2 sensor is damaged or has failed
 
TAC module is damaged or has failed
 

Trouble Code: P1281



Accelerator Pedal Position Sensor 2 Range/Performance

Possible Causes:



TP2 sensor connector is contaminated, oily or contains water
 
TP2 sensor signal, ground or VREF circuit has high resistance
 
TP2 sensor VREF circuit is open, shorted to ground or to B+
 
TP2 sensor signal or ground circuit has high resistance
 
TP2 sensor is damaged or has failed
 
TAC module is damaged or has failed
 

Trouble Code: P1285



Accelerator Pedal Position Sensor 3 Circuit Malfunction

Possible Causes:



APP3 sensor connector is contaminated, oily or contains water
 
APP3 sensor signal, ground or VREF circuit high resistance
 
APP3 sensor VREF circuit is open, shorted to ground or to B+
 
APP3 sensor signal or ground circuit has high resistance
 
APP3 sensor or the TAC module is damaged or has failed
 

Trouble Code: P1286



Accelerator Pedal Position Sensor 3 Range/Performance

Possible Causes:



APP3 sensor connector is contaminated, oily or moisture
 
APP3 sensor signal, ground or VREF circuit high resistance
 
APP3 sensor signal or ground circuit has high resistance
 
APP3 sensor or the TAC module is damaged or has failed
 

Trouble Code: P1336



CKP Sensor System Variation Not Learned

Possible Causes:



Set the parking brake and block the drive wheels for safety.
 
Verify the hood is closed.
 
Read the trouble codes. If a code is set, refer to that code.
 
Start the engine. Allow engine temperature to reach at least 158ºF (70ºC). Then key off.
 
Select Crankshaft Position Variation Learn procedure on Scan Tool & start the vehicle.
 
Apply the brake pedal firmly and verify the selector is in Park.
 
Increase accelerator pedal position until fuel cutoff is reached at the test rpm (e.g., 5150). Quickly release the accelerator pedal after fuel cutoff is reached. The CKP system variation compensating values are learned when the engine speed (rpm) decreases back to idle speed and the procedure terminates.
 
Read the trouble codes and recheck for DTC P1336.
 
If DTC P1336 runs and passes, the CKP system variation "learn" procedure is complete. If not, look for other codes. If no codes are set, repeat the test procedure.
 

Trouble Code: P1380



Misfire Detected, Rough Road Data Not Available

Possible Causes:



Use the Freeze Frame/Failure Records data to help find the cause on an intermittent fault. If the code cannot be duplicated, the data in the Freeze Frame/Failure Records can determine how many miles since the code set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the Freeze Frame conditions (i.e., load, engine and vehicle speed, temperature etc.). This will isolate when the code set.
 
Service the ABS before diagnosing a misfire because an actual engine misfire may or may not exist. Also, an actual engine misfire may have occurred during an ABS malfunction.
 
Determine if the vehicle was driven on a rough road, and the ABS could not detect this due to a malfunction. The PCM may interpret variations in crankshaft speed caused by the rough road as a misfire without an actual engine misfire present.
 
Refer to Diagnostic System Check for Antilock Brake System
 
Refer to Diagnostic System Check for the Engine Controls
 

Trouble Code: P1404



EGR Valve Closed Position Performance

Possible Causes:



EGR sensor signal circuit is shorted to VREF (5v)
 
EGR sensor ground circuit is open or has high resistance
 
EGR sensor is damaged or has failed (sensor/solenoid unit)
 
EGR valve pintle or valve seat contains carbon deposits
 
PCM has failed
 
TSB 01-06-04-043 contains a repair procedure for this code
 

Trouble Code: P1432



Fuel Pressure Sensor Circuit Low Input

Possible Causes:



Fuel tank pressure sensor is sticking or it is damaged
 
Fuel tank pressure sensor signal circuit is shorted to ground
 
Fuel tank pressure sensor is damaged or it has failed
 
PCM has failed
 

Trouble Code: P1433



Fuel Pressure Sensor Circuit Low Input

Possible Causes:



Fuel tank pressure sensor is sticking or it is damaged
 
Fuel tank pressure sensor signal circuit is shorted to ground
 
Fuel tank pressure sensor is damaged or it has failed
 
PCM has failed
 

Trouble Code: P1514



Throttle Body Performance

Possible Causes:



Inspect the throttle blade for damage and/or proper installation
 
Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple codes can set with no circuit or component faults apparent during diagnostic testing.
 
Physically and visually inspect the throttle body assembly, and throttle position sensor for damage and/or a loose mounting. Move the throttle blade from closed to wide open position without applying too much force. The throttle blade should move smoothly through the full range and should return to a slightly open position on its own.
 
If the TAC module detects a fault in the system, it may set more than one related code because of the many redundant tests that run continuously on this system. Locating and repairing one individual condition may fix more than one code.
 

Trouble Code: P1515



Control Module Throttle Actuator Position Performance

Possible Causes:



Throttle actuator motor CKT 1 is open, shorted to ground or B+
 
Throttle actuator motor CKT 2 is open, shorted to ground or B+
 
Throttle actuator motor is damaged or has failed
 
Throttle actuator motor control module has failed
 
TSB 00-06-04-035 contains a repair procedure for this code
 

Trouble Code: P1516



TAC Module Throttle Actuator Position Performance

Possible Causes:



TAC motor CKT 1 or CKT 2 is open, shorted to ground or B+
 
Throttle actuator motor CKT 1 is shorted to CKT 2
 
Throttle actuator motor control module has failed
 
TSB 03-04-06-034 contains a repair procedure for this code
 

Trouble Code: P1517



Throttle Actuator Control Module Performance

Possible Causes:



Test the charging system output (low voltage can set this code)
 
Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple codes may set without any circuit or component conditions found during diagnostic testing.
 
When the TAC module detects a fault condition, several TAC related codes set because there are redundant tests running.
 
TAC module has failed
 

Trouble Code: P1518



Throttle Actuator Control Module Serial Data Malfunction

Possible Causes:



DTC P1518 sets if the battery voltage is low. If the customer's concern is slow cranking or no crank due to low battery voltage, ignore the DTC P1518. Clear codes and retest.
 
DTC P1518 also 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 (e.g., Brake & Cruise) for the fault.
 
DTC P1518 sets if the TAC module power circuit is shorted to a B+ supply circuit. The TAC module stays powered-up when the ignition switch is turned off. When the key on, the TAC module is powered-up before the PCM gets power. DTC 1518 is set because the TAC module did not detect signals from the PCM.
 
TAC module has failed
 

Trouble Code: P1621



Control Module Long Term Memory Performance

Possible Causes:



Perform the Diagnostic System Check for Engine Controls
 
The PCM needs to be replaced and then reprogrammed
 

Trouble Code: P1626



Theft Deterrent Fuel Enable Signal Not Received

Possible Causes:



Check the serial data circuit for poor connections at the PCM
 
Perform the Powertrain Onboard Diagnostic System Check
 
Perform the Theft Deterrent Diagnostic System Check
 
TSB 77-65-31 contains a repair procedure for this code
 

Trouble Code: P1631



Theft Deterrent - Start Enable Signal Not Correct

Possible Causes:



Refer to Diagnostic System Check for Theft Deterrent Module
 
Perform the Powertrain Onboard Diagnostic System Check
 
TSB 77-65-31 contains a repair procedure for this code
 

Trouble Code: P1635



5-Volt Reference 1 Circuit Malfunction

Possible Causes:



5v VREF circuit is shorted to sensor ground or chassis ground
 
5v VREF circuit, MAP or EGR sensor circuit is shorted to (B+)
 
5v VREF circuit shorted to EGR sensor High signal circuit
 
EGR solenoid valve (and sensor) is damaged or has failed
 
PCM has failed
 

Trouble Code: P1637



Generator 'L' Terminal Circuit Malfunction

Possible Causes:



A Scan Tool should display Inactive for the 'L' Terminal and 10-40% for the 'F' Terminal with the ignition "on". With the engine running, the display should indicate the 'L' Terminal is Active and the 'F' Terminal is higher than 5% on the tool display.
 
Generator 'L terminal circuit shorted to ground or to power (B+)
 
Generator 'F' terminal circuit is open or shorted to ground
 
Generator is damaged or has failed or the PCM has failed
 

Trouble Code: P1638



Generator 'F' Terminal Circuit Malfunction

Possible Causes:



Generator connector is damaged or has high resistance
 
Generator field duty cycle signal circuit is open or shorted
 
Generator is damaged or has failed
 
PCM has failed
 

Trouble Code: P1639



5-Volt Reference 2 Circuit Malfunction

Possible Causes:



5v VREF circuit is shorted to sensor ground or chassis ground
 
5v VREF circuit, FTP or TP sensor circuit is shorted to (B+)
 
5v VREF circuit shorted to FTP or TP sensor signal circuit
 
FTP sensor or TP sensor is damaged or PCM has failed
 

Trouble Code: P1680



Powertrain Control Module Internal Malfunction

Possible Causes:



Clear the codes and then recheck for this trouble code. If the same code resets, the PCM is damaged and must be replaced (and the new PCM must be programmed) to repair this code.
 

Trouble Code: P1681



Powertrain Control Module Internal Malfunction

Possible Causes:



Clear the codes and then recheck for this trouble code. If the same code resets, the PCM is damaged and must be replaced (and the new PCM must be programmed) to repair this code.
 

Trouble Code: P1683



Powertrain Control Module Internal Malfunction

Possible Causes:



Clear the codes and then recheck for this trouble code. If the same code resets, the PCM is damaged and must be replaced (and the new PCM must be programmed) to repair this code.
 

Trouble Code: P2066



Secondary Fuel Sensor Signal Range/Performance

Possible Causes:



Perform the I/P Cluster Diagnostic System Check
 
Check the fuel tank for signs of foreign material (i.e., ice)
 
Fuel level sender is malfunctioning (check the fuel strainer to determine if it is interfering with the sender float arm - sticking)
 
Fuel level sensor is damaged or it has failed
 

Trouble Code: P2067



Secondary Fuel Level Sensor Circuit Low Input

Possible Causes:



Perform the I/P Cluster Diagnostic System Check
 
Fuel level sensor connector is damaged or shorted
 
Fuel level sensor signal circuit is shorted to ground
 
Fuel level sensor is damaged or it has failed
 

Trouble Code: P2068



Secondary Fuel Level Sensor Circuit High Input

Possible Causes:



Perform the I/P Cluster Diagnostic System Check
 
Fuel level sensor connector is damaged, open or shorted
 
Fuel level sensor signal circuit is open or shorted to power
 
Fuel level sensor is damaged or it has failed
 

Trouble Code: P2108



Throttle Actuator Control Module Internal Data Test Failed

Possible Causes:



TAC module is damaged or it has failed
 

Trouble Code: P2120



Accelerator Pedal Position Sensor 1 Signal Performance

Possible Causes:



APP sensor connector is damaged, open or shorted
 
APP1 sensor signal circuit is open or shorted to ground
 
APP1 sensor signal circuit is shorted to APP sensor 2 circuit
 
APP1 sensor signal circuit is open or shorted to VREF (5v)
 
APP sensor is damaged or it has failed
 
TAC module is damaged or it has failed
 

Trouble Code: P2121



Accelerator Pedal Position Sensor 1-2 Correlation Malfunction

Possible Causes:



APP sensor connector is damaged, open or shorted
 
APP1 sensor low reference circuit is open or high resistance
 
APP1 sensor VREF circuit is open or shorted to ground
 
APP sensor is damaged or it has failed
 
TAC module is damaged or it has failed
 

Trouble Code: P2125



Accelerator Pedal Position Sensor 2 Circuit Malfunction

Possible Causes:



APP1 sensor signal circuit is open or shorted to ground
 
APP1 sensor signal circuit is shorted to APP sensor 2 circuit
 
APP1 sensor signal circuit is open or shorted to VREF (5v)
 
APP sensor is damaged, or the TAC module is damaged or it has failed
 

Trouble Code: P2135



Throttle Position Sensor 1-2 Correlation Error

Possible Causes:



TP1 sensor signal circuit shorted to TP sensor signal 2 circuit
 
TP1 sensor signal circuit is shorted to the low reference circuit
 
TP2 sensor signal circuit is shorted to the low reference circuit
 
Throttle body assembly is damaged or it has failed
 

Trouble Code: P2146



Fuel Pump Relay Circuit Malfunction (Injectors 1, 4, 6 or 7)

Possible Causes:



Refer to repair information for P0201, P0204, P0206 or P0207
 
FICM (module) has failed (when P2146 is set all by itself)
 

Trouble Code: P2149



Fuel Pump Relay Circuit Malfunction (Injectors 2, 3, 5 or 8)

Possible Causes:



Refer to repair information for P0202, P0203, P0205 or P0208
 
FICM (module) has failed (when P2149 is set all by itself)
 

Trouble Code: P2665



AF Low Pressure Lock-Off Solenoid Circuit Malfunction

Possible Causes:



LPL solenoid control circuit is open or shorted to ground
 
LPL solenoid relay power circuit is open (test the AFS fuse)
 
LPL solenoid relay is damaged or it has failed
 
AF control module has failed
 

Trouble Code: U1000



Class 2 Communication Malfunction

Possible Causes:



Class 2 circuit is open, shorted to ground or shorted to power
 
PCM ignition power circuit(s) has a high resistance condition
 
PCM main ground circuit(s) has a high resistance condition
 
SDM (module) could be shorted pulling the voltage low
 

 
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