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

5.3L V8 VIN T Std 4

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Trouble Code: P1025



CNG Fuel Injector 5 Circuit Malfunction

Possible Causes:



CNG fuel injector 5 control circuit is open or shorted to ground
 
CNG fuel injector 5 is damaged or it has failed
 
FICM has failed
 

Trouble Code: P1026



CNG Fuel Injector 6 Circuit Malfunction

Possible Causes:



CNG fuel injector 6 control circuit is open or shorted to ground
 
CNG fuel injector 6 is damaged or it has failed
 
FICM has failed
 

Trouble Code: P1027



CNG Fuel Injector 7 Circuit Malfunction

Possible Causes:



CNG fuel injector 7 control circuit is open or shorted to ground
 
CNG fuel injector 7 is damaged or it has failed
 
FICM has failed
 

Trouble Code: P1028



CNG Fuel Injector 8 Circuit Malfunction

Possible Causes:



CNG fuel injector 8 control circuit is open or shorted to ground
 
CNG fuel injector 8 is damaged or it has failed
 
FICM has failed
 

Trouble Code: P1106



MAP Sensor Circuit Intermittent High Input

Possible Causes:



MAP sensor signal circuit is shorted to VREF (intermittent fault)
 
MAP sensor ground circuit is open (intermittent fault)
 
MAP sensor is damaged or has failed
 
PCM has failed
 

Trouble Code: P1107



MAP Sensor Circuit Intermittent Low Input

Possible Causes:



MAP sensor signal circuit is shorted to VREF (intermittent fault)
 
MAP sensor ground circuit is open (intermittent fault)
 
MAP sensor is damaged or has failed
 
PCM has failed
 

Trouble Code: P1111



IAT Sensor Circuit Intermittent High Input

Possible Causes:



IAT sensor signal circuit is open (intermittent fault)
 
IAT sensor ground circuit is open (intermittent fault)
 
IAT sensor is damaged (an intermittent "open" condition)
 
PCM has failed
 

Trouble Code: P1112



IAT Sensor Circuit Intermittent Low Input

Possible Causes:



IAT sensor signal circuit is open (intermittent fault)
 
IAT sensor ground circuit is open (intermittent fault)
 
IAT sensor is damaged (an intermittent "open" condition)
 
PCM has failed
 

Trouble Code: P1114



ECT Sensor Circuit Intermittent Low Input

Possible Causes:



ECT sensor signal circuit shorted to ground (intermittent fault)
 
ECT sensor has failed (possible intermittent shorted condition)
 
PCM has failed
 

Trouble Code: P1115



ECT Sensor Circuit Intermittent High Input

Possible Causes:



ECT sensor signal circuit is open between the sensor and PCM
 
ECT sensor ground circuit is open between sensor and PCM
 
ECT sensor has failed (possible intermittent "open" condition)
 
PCM has failed
 

Trouble Code: P1120



TP Sensor 1 Circuit Malfunction

Possible Causes:



TP1 sensor signal circuit is open, shorted to ground or to power
 
TP1 sensor VREF circuit is open or shorted to ground or to B+
 
TP1 sensor ground circuit has a high resistance condition
 
TP1 sensor is damaged or has failed
 

Trouble Code: P1122



TP Sensor Circuit Intermittent High Input

Possible Causes:



TP sensor signal circuit is shorted to VREF (intermittent fault)
 
TP sensor ground circuit is open (an intermittent fault)
 
TP sensor is damaged or has failed (possible intermittent open)
 
PCM has failed
 

Trouble Code: P1125



Accelerator Pedal Position System Malfunction

Possible Causes:



APP sensor connector contaminated with oil or moisture (this condition can cause signal "tracking" between the circuits)
 
When the TAC module detects a fault within the TAC system, it may set more than one code. This is due to the redundant tests run continuously on this system. Locating and repairing a single fault may correct more than one code. Keep this in mind as you review the Captured Info available with a Scan Tool.
 
Refer to the related TAC System trouble codes
 

Trouble Code: P1133



HO2S-11 (Bank 1 Sensor 1) Insufficient Switching

Possible Causes:



Air leaks present in the exhaust manifold or the exhaust pipes
 
Fuel pressure is too high (i.e., causing a rich air fuel mixture)
 
HO2S may be contaminated (due to improper fuel or silicone)
 
HO2S signal high or low reference circuit has high resistance
 
HO2S heater element has failed, or the heater circuit is open
 
PCM has failed
 

Trouble Code: P1134



HO2S-11 (Bank 1 Sensor 1) Transition Time Ratio

Possible Causes:



Air leaks present in the exhaust manifold or the exhaust pipes
 
HO2S may be contaminated (due to improper fuel or silicone)
 
HO2S signal low reference circuit has high resistance
 
HO2S heater element has failed, or the heater circuit is open
 
PCM has failed
 

Trouble Code: P1153



HO2S-21 (Bank 2 Sensor 1) Insufficient Switching

Possible Causes:



Air leaks present in the exhaust manifold or the exhaust pipes
 
Fuel pressure is too high (i.e., causing a rich air fuel mixture)
 
HO2S may be contaminated (due to improper fuel or silicone)
 
HO2S signal high or low reference circuit has high resistance
 
HO2S heater element has failed, or the heater circuit is open
 
PCM has failed
 

Trouble Code: P1154



HO2S-21 (Bank 2 Sensor 1) Transition Time Ratio

Possible Causes:



Air leaks present in the exhaust manifold or the exhaust pipes
 
HO2S may be contaminated (due to improper fuel or silicone)
 
HO2S signal low reference circuit has high resistance
 
HO2S heater element has failed, or the heater circuit is open
 
PCM has failed
 

Trouble Code: P1172



Secondary Fuel Pump Insufficient/No Fuel Flow

Possible Causes:



Fuel tank level is too low (must be within 25-75% to test relay)
 
Secondary F/P relay power circuit is open (test the ENG1 fuse)
 
Secondary F/P relay control circuit is open, shorted to ground or shorted to power
 
Secondary F/P relay is damaged or has failed
 
PCM has failed
 

Trouble Code: P1201



Gas Mass Sensor Range/Performance

Possible Causes:



Air filter or air inlet duct is clogged or restricted
 
Air leaks in the exhaust pipes or manifold, or the HO2S location
 
Base engine problem (i.e., engine compression, vacuum leak)
 
CNG system fuel pressure is incorrect
 
PCV system problem (i.e., PCV vacuum hose or valve leaking)
 
EVAP canister purge system malfunction
 
Gasoline contaminated engine oil
 
Fuel pressure regulator damage or leaking
 
PCM has failed
 

Trouble Code: P1207



FICM PWM Signal To PCM Circuit Malfunction

Possible Causes:



FICM sensor PWM signal circuit is open or shorted to ground
 
FICM is damaged or it has failed
 
PCM has failed
 

Trouble Code: P1215



High Pressure Or Low Pressure Lockout, MIL, NGO Circuit Malfunction

Possible Causes:



Natural Gas Output Enable, High Pressure Lockout, Low Pressure Lockout or MIL control circuit is open, shorted to ground or shorted to system power
 
Alternative Fuels ECU is damaged or has failed
 

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: 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
 

 
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