IAT – Intake Air Temperature sensor Harley Davidson Check Engine – Ignition Diagnostic Codes

Below covers basic Harley Davidson diagnostics, and most of the diagnostic codes for evaluating possible issues.

All Harley Davidson System Problems – Fall into at least one of three general categories:

Harley Davidson No Start – The engine cranks over freely, but will not start. This does not include situations where the engine will not crank, such as a bad starter, dead battery, etc. This condition assumes that all obvious checks (fuel in tank, etc.) have been made.

Harley Davidson Poor Performance – The engine starts but there are performance problems.These problems may include poor fuel economy, rough idle, engine misfire, engine hesitation, severe spark knock, etc.

Harley Davidson Check Engine Lamp – The check engine lamp indicates the ignition control module (ICM) has determined a fault condition exists. There may also be starting or performance problems.


To resolve Harley Davidson system problems, five basic steps are involved. In order of occurrence, they are:

  • Check for diagnostic trouble codes (DTCs) by observing check engine.
  • Retrieve DTCs using Speedometer self diagnostics.
  • Diagnose system problems. This involves using special tools and the diagnostic flow charts in this section.
  • Correct problems through the replacement and/or repair of the affected components.
  • After repairs – Clear DTCs and confirm proper vehicle operation as indicated by the check engine lamp.

To diagnose Harley Davidson system problems, begin by observing the behavior of the check engine lamp. When the ignition switch is turned ON, the check engine lamp will illuminate for approximately four seconds and then turn off. If the check engine lamp is not illuminated at key ON or if it fails to turn OFF after the initial four second period. If the check engine lamp illuminates late (after 20 seconds), the problem is most likely a serial data bus failure. Test for diagnostic trouble codes (DTCs) using speedometer self diagnostics. If the check engine lamp fails to turn OFF after the initial four second period, a problem exists in the instrumentation. After the check engine lamp turns off following the first four-second illumination period, one of three events may occur:

  • The lamp remains off. This indicates there are no current fault conditions or stored DTCs currently detected by the ICM.
  • The lamp remains off for only four seconds and then illuminates for an eight-second period. This indicates a DTC is stored, but no current DTC exists.
  • The lamp remains off for only four seconds and then is illuminated beyond the eight-second period. This indicates a current DTC exists.

NOTE – Harley Davidson DTCs relating to the ignition coil can only be fully diagnosed during actuation. For example, a problem with the ignition coil will be considered a current fault even after the problem is corrected, since the ignition control module will not know of its resolution until after the coil is exercised by vehicle start sequence. In this manner, there may sometimes be a false indication of the current DTC.

To diagnose Harley Davidson turn signal module (TSM) or turn signal security module (TSSM) system problems, begin by observing the behavior of the security lamp. When the ignition switch is turned ON, the security lamp will illuminate for approximately four seconds and then turn off. If the security lamp is not illuminated at Key ON, the problem is likely to be an instrument failure. If the security lamp illuminates late (after 20 seconds), the problem is most likely a serial data bus failure.

There are two types of Harley Davidson DTCs: current and historic. If a DTC is stored, it can be read using either Digital Technician or the speedometer self diagnostics. All DTCs reside in the memory of the ICM or TSM/TSSM until the DTC is cleared using the speedometer self diagnostics or a total of 50 trips has elapsed. A trip consists of a start and run cycle, the run cycle lasting at least 30 seconds. After the 50 trip retention period, the DTC is automatically erased from memory providing that no subsequent faults of the same type are detected in that period.

Speedometer Self Diagnostics:

  • Turn Ignition switch to OFF & Run/Stop switch is to Run.
  • Push odometer reset button in & hold.
  • Turn ignition switch to Ignition and release odometer reset button. Background lighting sould illuminate, speedometer needle should sweep its full range and indicator lamps (battery, security, low fuel, check engine and cruise) should illuminate. The word diag should then appear.
  • Push the odometer reset button once and you will see the selection menu “PSSPt” with the first P flashing.
  • Each letter represents an area of the diagnostics module. The module that is flashing is the one you are going to check. To move from one letter (module) to the next, you push the odometer reset button one time. Example: from P to S to SP to T and back to P.
  • To get the DTC within an area of diagnostics, push and hold the odometer reset button in for 5 seconds and release. If there are any DTC’s the code will be displayed or the word ‘NONE’ will appear if there are no DTC’s.
  • Push the odometer reset button again to view additional codes if they exist -Record the codes.
  • Press and release the odometer reset button to continue to the next module.

NOTE: If Harley Davidson DTC’s are not to be cleared, Press and release the odometer reset button. Part number of module will be displayed. To determine if a code is current or historic, clear the displayed code by pushing in and holding the odometer reset button (longer than 5 seconds) until ‘CLEAR’ comes up. Release the odometer reset button. Turn OFF the ignition switch. Run your bike and shut it down then recheck the DTC’s again by repeating above steps. If the code is current it will reappear.


B0563 Battery Voltage High TSM/TSSM
B1004 Fuel Level Sending Unit Low Instruments
B1005 Fuel Level Sending Unit High/Open Instruments
B1006 Accessory Line Overvoltage Instruments
B1007 Ignition Line Overvoltage Instruments
B1008 Reset Switch Closed Instruments
B1131 Alarm Output Low TSM/TSSM
B1132 Alarm Output High TSM/TSSM
B1134 Starter Output High TSM/TSSM
B1135 Accelerometer Fault TSM/TSSM
B1151 Sidecar BAS Low TSM/TSSM
B1152 Sidecar BAS High TSM/TSSM
B1153 Sidecar BAS Out of Range TSM/TSSM
P0106 MAP Sensor Rate of Range Error Carb
P0107 Map Sensor Failed Open/Low Carb
P0107 Map Sensor Open/Low EFI
P0108 Map Sensor Failed High Carb
P0108 Map Sensor High EFI
P0112 IAT Sensor Voltage Low EFI
P0113 IAT Sensor Voltage Open/High EFI
P0117 ET Sensor Voltage Low EFI
P0118 ET Sensor Voltage Open/High EFI
P0122 TP Sensor Open/Low EFI
P0123 TP Sensor High EFI
P0261 Front Injector Open/Low EFI
P0262 Front Injector High EFI
P0263 Rear Injector Open/Low EFI
P0264 Rear Injector High EFI
P0373 CKP Sensor Intermittent Carb
P0373 CKP Sensor Intermittent EFI
P0374 CKP Sensor Not Detected Carb
P0374 CKP Sensor Synch Error EFI
P0501 VSS Low Carb
P0501 VSS Low EFI
P0502 VSS High/Open Carb
P0502 VSS High/Open EFI
P0505 Loss of Idle Sped Control EFI
P0562 Battery Voltage Low Carb
P0562 Battery Voltage Low EFI
P0563 Battery Voltage High Carb
P0563 Battery Voltage High EFI
P0602 Calibration Memory Error Carb
P0603 EEPROM Failure Carb
P0604 RAM Failure Carb
P0605 Program Memory Error Carb
P0605 ECM Flash Error EFI
P0607 Converter Error Carb
P1001 System Relay Coil Open/Low EFI
P1002 System relay Coil High/Shorted EFI
P1003 System relay Contacts Open EFI
P1004 System Relay Contacts Closed EFI
P1009 Incorrect Password Carb
P1009 Incorrect Password EFI
P1010 Missing Password Carb
P1010 Missing Password EFI
P1351 Front Ignition Open/Low Carb
P1351 Front Ignition Open/Low EFI
P1352 Front Ignition Coil High/Shorted Carb
P1352 Front Ignition Coil High/Shorted EFI
P1353 Front Cylinder No Combustion EFI
P1354 Rear Ignition Coil Open/Low Carb
P1354 Rear Ignition Coil Open/Low EFI
P1355 Rear Ignition Coil High/Shorted Carb
P1355 Rear Ignition Coil High/Shorted EFI
P1356 Rear Cylinder No Combustion EFI
P1357 Intermittent Secondary Front EFI
P1358 Intermittent Secondary Rear EFI
U1016 Loss of ICM/ECM Serial Data Instruments
U1016 Loss of ECM Serial Data – Vehicle Speed
U1064 Loss of TSM/TSSM Serial Data Carb
U1064 Loss of TSM/TSSM Serial Data EFI
U1064 Loss of TSM/TSSM Serial Data Instruments
U1097 Loss of Speedometer Serial data Carb
U1097 Loss of Speedometer Serial data EFI
U1097 Loss of Speedometer Serial data TSM/TSSM
U1255 Missing Message at Speedometer EFI
U1255 Serial Data Error/Missing Message EFI
U1255 Serial Data Error/Missing Message Instruments
U1255 Serial Data Error/Missing Message TSM/TSSM
U1300 Serial Data Low Carb
U1300 Serial Data Low EFI
U1300 Serial Data Low Instruments
U1300 Serial Data Low TSM/TSSM
U1301 Serial Data Open/High Carb.
U1301 Serial Data Open/High EFI
U1301 Serial Data Open/High Instruments
U1301 Serial Data Open/High TSM/TSSM

Harley Davidson Various Definitions

P = ECM/ICM (Electronic Control Module (EFI) / (Ignition Control Module, ‘Carbureted’)

S = TSM/TSSM (Turn Signal/ Turn Signal Security Module)

SP = Speedometer

T = Tachometer

AFR – Air Fuel Ratio

ATS – Air Temperature Sensor

BAS – Bank Angle Sensor

CCM – Cruise Control Module

CKP – Crank Position Sensor. The CKP generates an ‘AC signal’ which is sent to the ECM where it is used to reference engine position (TDC) and speed.

DTC – Diagnostic Trouble Codes

ECM – Electronic Control Module. (The Computer) Computes the spark advance for proper ignition timing and fuel control based on sensor inputs (from CKP, MAP & TP sensors) and controls the low-voltage circuits for the ignition coils and injectors. The dwell time for the ignition coil is also calculated in the microprocessor and is dependent upon battery voltage. The programmed dwell feature gives adequate spark at all speeds.

ECT – Engine Coolant Temperature. Sensor also controls the cooling fan relay that provides 12 Vdc to the fans.

EFI – Electronic Fuel Injection

EFP – Electronic Fuel Pump

ET – Engine Temperature sensor

FI – Fuel Injectors

FPR – Fuel Pressure regulator

IAC – Idle Air Control actuator


ISS – Ion Sensing System detonation detection

MAP – manifold Absolute Pressure sensor. The MAP sensor monitors the intake manifold pressure (vacuum) and sends the information to the ECM.

The EMC then adjusts the spark and fuel-timing advance curves for optimum performance. TP – Throttle Position Sensor

TSM/TSSM (Turn Signal/ Turn Signal Security Module)

VE – Volume Efficiency

VSS – Vehicle Speed Sensor. Used as an input for idle speed control

If Harley Davidson speedometer reads ‘BUS Er’ with the ignition key switch turned ON (engine stop switch at RUN with the engine off), check serial data line for an open or short to ground between diagnostic link [91A] terminal 3 and ICM connector terminal 12. Check for an open diagnostic test terminal between diagnostic link connector terminal 3 and ICM. With ignition key switch turned ON, transmit data should be typically 0.6-0.8 volts. The range of acceptable operation of the serial data line is 0-7.0 volts. For a quick check of speedometer function, a ‘wow’ test can be performed. Press and hold odometer reset switch then turn ignition switch ON. Release reset switch. Background lighting should illuminate, gauge needles should sweep their full range of motion, and check engine, battery and security indicator lamps should illuminate. The security lamp may illuminate even if the vehicle is not equipped with a security system. If instrument module fails ‘wow’ test, check for battery, ground, ignition and accessory wiring to speedometer.

Harley Davidson engine cranks but will not start – Is there fresh fuel in tank? Are spark plug wires firmly connected to coil terminals? YES to both then – Check for continuity to ground at breakout box terminal 7 (black). Wiggle harness during continuity check. Check for battery voltage at breakout box terminal 5 (black) while wiggling harness. Check the condition of the battery. Perform a voltage test and recharge if below 12.60V. Check battery connections and perform load test – If it fails replace the battery. Remove spark plug cable from spark plug. Visually check condition of plug. Attach cable to SPARK TESTER – Clip tester to cylinder head bolt. While cranking engine, look for spark. Repeat procedure on other spark plug cable. If NO spark check the resistance of each spark plug cable that did not fire the spark tester. Also check for faulty plug wire connections and wire boots for carbon tracking.

Spark will not be present when cranking with both spark plugs removed. When checking for spark, use SPARK TESTER with both spark plugs installed and one spark plug wire connected to spark tester. Reinstall spark plug cable and repeat procedure on other spark plug cable. Perform spark plug cable resistance test. Remove spark plug cable from spark plug and ignition coil. For best results, use a needle nose pliers for removal/installation on coil. Gently grasp cable as close to terminals as possible. Using an ohmmeter, touch probes to terminals on each end of plug wire. Reinstall and repeat procedure on other spark plug cable. This test can also be performed by substituting a known good coil for one causing the no spark condition. The coil does not require full installation to be functional.

The manifold absolute pressure sensor is supplied 5 volts from the ignition control module and sends a signal back to the ignition control module. This signal varies in accordance with engine vacuum and atmospheric barometric pressure. Changes in barometric pressure are influenced by weather and altitude. With the MAP sensor disconnected, the ignition control module should recognize a low voltage. If low voltage is observed, the ignition control module and harness are not at fault. Gently place a jumper wire across MAP Sensor connector terminals B and C using HARNESS CONNECOR TEST KIT, gray male probes and patch cord. With the jumper in place, the ignition control module should recognize a high voltage. MAP sensor output check. Using the VACUUM PUMP, apply a vacuum to the pressure port of the MAP sensor. The signal voltage should lower as the vacuum is applied.

Crank Position Sensor: DTC P0371, P0372, P0374 – Check for intermittent connection, pinched or damaged wires, and loose CKP sensor fastener. Conditions found? Connect Breakout Box to harness only, leaving ignition control module disconnected. Measure resistance between terminal 8 and terminal 5 (black) on Breakout Box and terminal 9 (black) and terminal 5 of (black) on Breakout Box. Is resistance more than 1 megohm? NO – Connect DVOM to Terminals 8 and 9 at connector on Breakout Box. Set DVOM to AC volts and crank engine. Does DVOM read 1 VAC minimum during cranking? YES – Repairs are necessary.

Ignition Coil – Ignition coil DTCs will set if the ignition coil primary voltage is out of range.This could occur if there is an open coil or loss of power to the coil. If front and rear DTCs are set simultaneously, it is likely a coil power failure or a coil failure has occurred. The coil receives power from the engine run/stop switch. The ignition control module is responsible for turning on the coils by providing the ground to activate the coils, which in turn powers the coils.

The initial Harley Davidson diagnostic check is an organized approach to identifying a problem caused by an electronic control system malfunction. If no problems are found after completion of the initial diagnostic check, a comparison of running parameters may be used to help locate intermittents and out-of-specification sensors. If still NO conditions are found, and the engine won’t run. Then it may be mechanical failure – Things to check then would be compression, cam timing, and the fuel system. NOTE: Cranking the engine with test lamp in place of the ignition coil can sometimes cause a DTC P1351 or P1352 to be set. This condition is normal and does not by itself indicate a malfunction. Clear DTCs afterward.