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

6.5L V8 VIN F Auto 3

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Trouble Code: P0785



A/T 3-2 Shift Solenoid Circuit Malfunction (4L80-E)

Possible Causes:



3-2 shift solenoid control circuit is open or shorted to ground
 
3-2 shift solenoid control circuit is shorted to system power
 
3-2 shift solenoid power circuit is open (check the TRANS fuse)
 
3-2 shift solenoid is damaged or has failed
 
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 in this system, it may set more than one code (due to redundant tests running constantly)
 
Refer to the related TAC system trouble codes
 

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: P1214



Injection Pump Timing Offset

Possible Causes:



The PCM will only run the test if the TDC offset adjustment time set procedure has been activated. The vehicle will most likely not be brought in with this code in memory.
 
CKP sensor incorrectly installed or mounting tab is broken
 
Fuel injection pump is damaged or has failed (a new pump will need to be "timed" using the correct pump timing procedure)
 

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: P1216



Fuel Solenoid Response Time Too Short

Possible Causes:



Intermittent P0251, P0370, and P1216 codes may be caused by air entering the fuel system when fuel levels get below 1/8 of a tank during hard acceleration or turning maneuvers. Codes P0251, P0370, and P1216 may set if the vehicle has run out of fuel. Customer driving habits should be checked to determine if the vehicle has been performing in these manners. If the vehicle has performed in these conditions, bleed the fuel system of all air and then perform a complete vehicle test drive.
 
Injection pump timing circuit is open, shorted to ground or to B+
 
TSB 77-63-06A contains a repair procedure for this code
 

Trouble Code: P1217



Fuel Solenoid Response Time Too Long

Possible Causes:



Fuel solenoid driver power circuit is open (test FUEL SOL fuse)
 
Fuel solenoid high circuit is open or shorted to ground
 
Fuel solenoid low circuit is open
 
Fuel solenoid is damaged or has failed (solenoid may be weak)
 
Fuel solenoid driver has failed
 

Trouble Code: P1218



Injection Pump Calibration Circuit Malfunction

Possible Causes:



Fuel solenoid driver connections have a problem
 
Fuel solenoid is damaged or has failed
 
Fuel injection pump is damaged or has failed (a new pump will need to be "timed" using the correct pump timing procedure)
 

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: P1621



Control Module Long Term Memory Performance

Possible Causes:



Perform the Powertrain Onboard Diagnostic System Check
 
The PCM needs to be replaced
 

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: P1630



Theft Deterrent System - Learn Mode Enable

Possible Causes:



This DTC (PCM in learn mode) is used at the assembly plant, dealership or by other service personnel to indicate learn mode is enabled (i.e., the PCM is ready to lean a new password).
 
Perform Diagnostic System Check for Theft Deterrent System
 
Perform the Powertrain Onboard 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 Circuit Low Input

Possible Causes:



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

Trouble Code: P1639



5-Volt Reference Circuit Low Input

Possible Causes:



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

Trouble Code: P1641



MIL Control Circuit Malfunction

Possible Causes:



MIL control circuit is open, shorted to ground or to power (B+)
 
MIL (lamp) is damaged or failed (open circuit or missing)
 
MIL power circuit is open (check GAUGES fuse in fuse block)
 
PCM has failed
 

Trouble Code: P1643



Wait To Start Lamp Control Circuit Malfunction

Possible Causes:



Wait to start lamp control circuit is open, shorted to ground or shorted to power (B+)
 
Wait to start lamp power circuit is open (check GAUGES fuse)
 
Wait to start "bulb" is open or is missing
 
PCM has failed
 

Trouble Code: P1653



EGR Vent Solenoid Control Circuit Malfunction

Possible Causes:



Vent solenoid control circuit is open, shorted to ground or to B+
 
Vent solenoid power circuit is open (check the ENG1 fuse)
 
Vent solenoid is damaged, or the PCM has failed
 

Trouble Code: P1654



Service Throttle Soon Lamp Control Circuit Malfunction

Possible Causes:



STS lamp control circuit is open, shorted to ground or to system power (B+)
 
STS lamp (bulb) is open or missing
 
STS lamp power circuit is open (power is through the IPC)
 
PCM has failed
 

Trouble Code: P1656



Wastegate Solenoid Control Circuit Malfunction

Possible Causes:



Waste solenoid circuit is open, shorted to ground or to power (B+)
 
Wastegate solenoid power circuit is open (check ENG1 fuse)
 
Wastegate solenoid is damaged or has failed
 
PCM 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
 

Trouble Code: U1016



No Communication With Powertrain Control Module

Possible Causes:



PCM Class 2 circuit is open, shorted to ground or to B+
 
PCM ignition power circuit(s) has a high resistance condition
 
PCM main ground circuit(s) has a high resistance condition
 
PCM (module) may have failed and is pulling the circuit low
 

Trouble Code: U1026



Loss of ATC Class 2 Communication

Possible Causes:



Check for a loose connection at the ATC module
 
Test the main power and ground circuits to the ATC module
 
Check the Class 2 serial data circuit to the ATC module
 
ATC module may have failed
 

Trouble Code: U1041



Loss of Electronic Brake Controller Communication

Possible Causes:



Check for a loose connection at the EBCM (module)
 
Test the main power and ground circuits to the EBCM (module)
 
Check the Class 2 serial data circuit to the EBCM (module)
 
EBCM (module) may have failed
 

Trouble Code: U1048



No Communication With Rear Wheel Steering Control Module

Possible Causes:



RWSCM Class 2 circuit is open, shorted to ground or to B+
 
RWSCM ignition power circuit has a high resistance condition
 
RESCM main ground circuit(s) has a high resistance condition
 
RESCM (module) may have failed and is pulling the circuit low
 

Trouble Code: U1064



No Communication With Body Control Module

Possible Causes:



BCM Class 2 circuit is open, shorted to ground or to B+
 
BCM ignition power circuit has a high resistance condition
 
BCM main ground circuit(s) has a high resistance condition
 
BCM (module) may have failed and is pulling the circuit low
 

Trouble Code: U1088



No Communication With SDM (Restraint Module)

Possible Causes:



SDM Class 2 circuit is open, shorted to ground or to B+
 
SDM ignition power circuit has a high resistance condition
 
SDM main ground circuit(s) has a high resistance condition
 
SDM (module) may have failed and is pulling the circuit low
 

Trouble Code: U1092



Loss of VTD (Pass Lock) Communication

Possible Causes:



Check for a loose connection at the VTD module
 
Test the main power and ground circuits to the VTD module
 
Check the Class 2 serial data circuit to the VTD module
 
VTD module may have failed
 

Trouble Code: U1096



No Communication With Instrument Panel Cluster

Possible Causes:



IPC Class 2 circuit is open, shorted to ground or to B+
 
IPC ignition power circuit has a high resistance condition
 
IPC main ground circuit(s) has a high resistance condition
 
IPC (module) may have failed and is pulling the circuit low
 

Trouble Code: U1097



No Communication With Driver Information Center

Possible Causes:



DIC Class 2 circuit is open, shorted to ground or to B+
 
DIC ignition power circuit has a high resistance condition
 
DIC main ground circuit(s) has a high resistance condition
 
DIC (module) may have failed and is pulling the circuit low
 

Trouble Code: U1151



No Communication With Vehicle Interface Unit

Possible Causes:



VIU Class 2 circuit is open, shorted to ground or to B+
 
VIU ignition power circuit has a high resistance condition
 
VIU main ground circuit(s) has a high resistance condition
 
VIU (module) may have failed and is pulling the circuit low
 

Trouble Code: U1152



No Communication With HVAC Control Module

Possible Causes:



HVAC Class 2 circuit is open, shorted to ground or to B+
 
HVAC ignition power circuit has a high resistance condition
 
HVAC main ground circuit(s) has a high resistance condition
 
HVAC (module) may have failed and is pulling the circuit low
 

Trouble Code: U1193



Loss of Vehicle Immobilizer Module Communications

Possible Causes:



Test the main power and ground circuits to the VIM module for a loose connection
 
Check the Class 2 serial data circuit to the VIM module
 
VTD module may have failed
 

Trouble Code: U1255



Class 2 Communications 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
 

Trouble Code: U1305



Class 2 Data Link High or Low

Possible Causes:



Class 2 serial data line has either a high or low voltage condition on the circuit, and the module cannot identify the fault
 
One or more modules on Class 2 line has an short to power
 
One or more modules on the Class 2 line has a short to ground
 

 
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