Express, Savana, G1500, G2500, G3500, 1998-2005

7.4L V8 VIN J Auto 4

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Trouble Code: P1351



ICM Ignition Control Circuit High Input

Possible Causes:



ICM control circuit is open, shorted to ground or shorted to B+
 
ICM power circuit is open (check power from the ECM1 fuse)
 
ICM is damaged or has failed
 
PCM has failed
 

Trouble Code: P1361



ICM Ignition Control Circuit Low Input

Possible Causes:



IC timing control circuit is open or shorted to ground
 
IC timing control circuit is shorted to system power
 
IC bypass circuit is open or shorted to ground
 
IC module has failed
 
PCM has failed
 

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. 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: P1381



Misfire Detected - No Communication With The EBCM

Possible Causes:



Service the ABS before diagnosing a misfire because an actual engine misfire may not exist. Also, an actual engine misfire may have occurred during a period of ABS fault.
 
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 or system voltage
 
EGR sensor VREF circuit is shorted to system power
 
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: P1415



Secondary Air Injection System (Bank 1) Malfunction

Possible Causes:



Air hoses disconnected, loose, kinked or failed (a burnt hose)
 
AIR pump is damaged or has failed (inspect air pump for water)
 
AIR system check valves and/or pipes are damaged or leaking
 
PCM has failed
 

Trouble Code: P1416



Secondary Air Injection System (Bank 2) Malfunction

Possible Causes:



Air hoses disconnected, loose, kinked or failed (a burnt hose)
 
AIR pump is damaged or has failed (inspect air pump for water)
 
AIR system check valves and/or pipes are damaged or leaking
 
PCM has failed
 

Trouble Code: P1441



EVAP System Flow During Non-Purge

Possible Causes:



An improperly installed or damaged EVAP canister purge valve
 
A temporary blockage in the EVAP canister purge valve, purge pipe, or EVAP canister could cause an intermittent condition
 
FTP sensor is out-of-calibration, damaged or "skewed"
 
Purge solenoid valve is damaged or has failed
 
PCM has failed
 

Trouble Code: P1508



Idle Speed Low - IAC System Not Responding

Possible Causes:



Base engine problem causing a slow or unstable idle speed
 
Fuel system is too rich or too lean
 
IAC motor is damaged or has failed (it may be sticking)
 
Throttle body plate or bore contaminated with foreign material
 
Throttle body adjustment screw tampered with or damaged
 
Perform the IAC Reset procedure with the Scan Tool
 

Trouble Code: P1509



Idle Speed High - IAC System Not Responding

Possible Causes:



Base engine problem (engine vacuum leak or PCV valve leak)
 
Fuel system is too rich or too lean
 
IAC motor circuit open, shorted to ground or shorted to power
 
Throttle body adjustment screw tampered with or damaged
 
Perform the IAC Reset procedure with the Scan Tool
 

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:



Serial data circuit is open between VCM and VTD (Passlock) control module, or serial data circuit is shorted to ground or B+
 
Perform the Theft Deterrent System Check
 
Perform the Powertrain Onboard Diagnostic System Check
 

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 EOP 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: P1639



5-Volt Reference 2 Circuit Malfunction

Possible Causes:



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

Trouble Code: P1810



TFP Valve Position Switch Assembly (4L60-E, 4L65-E, 4L80-E)

Possible Causes:



TFP valve position switch signal circuit is open, grounded or shorted to another signal
 
TFP valve position switch is damaged or has failed
 
This code can set during fluid refilling. After refilling the fluid, cycle the key "off", then idle the engine for 20 seconds. Turn the key "off" and allow the PCM to power down.
 
This code can set due to low pump pressure or due to a stuck pressure regulator.
 
This code can set due to a rolled forward clutch piston seal. It may allow the PCM to see a 2.08:1 ratio (reverse) when the manual valve position is actually indicated in D4.
 
PCM has failed
 

Trouble Code: P1860



TCM PWM Solenoid Circuit Malfunction (4L60-E, 4L65-E, 4L80-E)

Possible Causes:



TCC solenoid control circuit is open or shorted to ground
 
TCC solenoid control circuit is shorted to system power (B+)
 
TCC solenoid power circuit is open (test TRANS or IGN fuse)
 
TCC solenoid is damaged or has failed
 
PCM has failed
 

Trouble Code: P1870



Transmission Component Slipping (4L60-E, 4L65-E, 4L80-E)

Possible Causes:



1-2 shift solenoid valve has sediment, damage or leaking seals
 
2-3 shift solenoid valve has sediment, damage or leaking seals
 
3-2 shift solenoid valve has sediment, damage or leaking seals
 
Valve body regulator apply valve stuck or regulator is scored
 
Torque converter front stator shaft bushing is worn, the stator roller clutch is not holding or it has external damage/leaks
 
Converter clutch valve is stuck or it is installed backwards
 
Converter clutch valve retaining ring is not positioned properly
 
Converter clutch outer valve spring is cocked
 
Pump to case gasket is not positioned properly
 
Orifice cup plugs are restricted or damaged
 
Over-tightened, or unevenly tightened pump body to cover bolts
 
TSB 02-07-30-001 contains a repair procedure for this code
 

Trouble Code: P1875



4WD Low Switch Circuit Fault (4L60-E, 4L65-E, 4L80-E)

Possible Causes:



4WD low switch signal circuit is open, shorted to ground or B+
 
4WD low switch 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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