Honda ECU Error Codes
Here's a handy chart for pulling your ECU codes. Pulling the code is a fairly easy process.
For 92+ Honda's and 94+ Acura's:
Before you can start reading the CEL (check engine light) in your dash, you need to 'jump' your ecu.
Locate the factory two-pin connector of brown and black wires near the ECU on Civics, del Sols, and Integras, or behind the center console for Preludes and Accords. Pull that 2-pin out of the main harness. Using a wire or paper clip as a jumper, connect the outputs of the harness together, so that the black wire and the brown wire make a circuit. Once this is jumped together, the dash will start the light show, so its a good idea to jump first, then turn to on.
For 88-91 Honda's and 86-93 Acura's:
The ECU's on these cars actually have a neat little window right on the computer case. No need to jump here- just turn it to on, and watch it right there through that window.
For both steps above, the output will be in a Morse code style of long and short lights. For example, 2 long, pause, 3 short is 23.
1- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
Oxygen Sensor "A" (Primary)
defective circuit or unplugged / defective sensor
2- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-89 86-87 n/a 85-87 85-91 n/a n/a
Oxygen Sensor "B"
defective circuit or unplugged / defective sensor
3- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
MAP Sensor (Manifold Absolute Pressure)
defective circuit or unplugged / defective sensor
4- Accord Civic CRV CRX Del Sol Odyssey Prelude
90-98 88-98 97-98 88-91 93-97 95-98 85-98
CKP Sensor (Crankshaft Position Sensor)
defective circuit or unplugged / defective sensor
5- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 * 86-98 97-98 85-91 93-97 96-98 85-98
MAP Sensor (Manifold Absolute Pressure)
mechanical problem / disconnected piping
* exc 94-95
6- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
ECT Sensor (Engine Coolant Temperature)
defective circuit or unplugged / defective sensor
7- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
TP Sensor (Throttle Position)
defective circuit or unplugged / defective sensor
8- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
TDC Sensor (Top Dead Center)
defective circuit or unplugged / defective sensor
9*- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98** 86-98 97-98 85-91 93-97 95-98 85-98
CYP Sensor (Cylinder)
defective circuit or unplugged / defective sensor
* not a valid code for any throttle body injection Hondas
** not a valid code for V-6 engines
10- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
IAT Sensor (Intake Air Temperature)
defective circuit or unplugged / defective sensor
12- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 * n/a 85-91 * n/a 95-98 85-98
EGR Lift Sensor (Exhaust Gas Recirculation)
defective circuit or unplugged / defective sensor
* not a valid code if car is not equipped with an EGR valve (some Civic models are not)
13- Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
BARO Sensor (Atmospheric Pressure)
defective circuit or unplugged / defective sensor
14- Accord Civic CRV CRX Del Sol Odyssey Prelude
88-98 88-98 97-98 88-91 93-97 95-98 88-98
IAC Valve (Idle Air Control)
defective circuit or unplugged / defective sensor
15- Accord Civic CRV CRX Del Sol Odyssey Prelude
90-95 88-95 n/a 88-91 93-95 95 88-95
Ignition Output Signal
missing or defective ignition output signal
16- Accord Civic CRV CRX Del Sol Odyssey Prelude
90-95 88-95 n/a 88-91 93-95 95 88-95
Fuel Injector System
defective circuit or unplugged / defective fuel injector
17- Accord Civic CRV CRX Del Sol Odyssey Prelude
88-98 88-98 97-98 88-91 93-97 95-97 88-98
VSS (Vehicle Speed Sensor)
defective circuit or unplugged / defective sensor
19- Accord Civic CRV CRX Del Sol Odyssey Prelude
n/a 88-95 n/a 88-91 93-97 n/a n/a
Automatic Transmission Lock Up Control Solenoid Valve
defective circuit or unplugged / defective solenoid valve
20- Accord Civic CRV CRX Del Sol Odyssey Prelude
90-98 88-98 97-98 88-91 93-97 95-98 92-98
Electrical Load Detector
defective circuit or unplugged / defective sensor
21*- Accord Civic CRV CRX Del Sol Odyssey Prelude
94-98 ** 92-95 n/a n/a 93-95 n/a 93-95
VTEC Solenoid Valve
defective circuit or unplugged / defective solenoid valve
* not a valid code if car does not have a VTEC engine
** not with V-6 engine
22*- Accord Civic CRV CRX Del Sol Odyssey Prelude
94-98 92-98 n/a n/a 93-97 98 93-98`
VTEC Oil Pressure Switch
defective circuit or unplugged / defective oil pressure switch
* not a valid code if car does not have a VTEC engine
23- Accord Civic CRV CRX Del Sol Odyssey Prelude
98 * 96-98 n/a n/a 94-97 n/a 92-98
KS (Knock Sensor)
defective circuit or unplugged / defective sensor
* not a valid code if V-6 engine
30- Accord Civic CRV CRX Del Sol Odyssey Prelude
90-98 * n/a n/a n/a n/a 95 92-98 *
Automatic Transmission Signal: "A" / SEAF / SEFA / TMA or TMB
defective circuit or unplugged / defective sensor
* not a valid code for 1996
31- Accord Civic CRV CRX Del Sol Odyssey Prelude
90-95 n/a n/a n/a n/a 95 92-95
Automatic Transmission Signal "B"
defective circuit or unplugged / defective sensor
41- Accord Civic CRV CRX Del Sol Odyssey Prelude
90-98 92-98 97-98 n/a 93-97 95-98 90-98
Primary Oxygen Sensor - Heater
circuit malfunction
43- Accord Civic CRV CRX Del Sol Odyssey Prelude
90-95 92-95 n/a n/a 93-95 95 90-95
Fuel Supply System
defective or malfunctioning fuel supply system
45- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
System Too Lean or Too Rich
malfunction in the fuel monitoring systems
48- Accord Civic CRV CRX Del Sol Odyssey Prelude
98 92-98 n/a n/a n/a n/a n/a
LAF Sensor (Lean Air Fuel)
defective circuit or unplugged / defective sensor
54- Accord Civic CRV CRX Del Sol Odyssey Prelude
96 96-98 97-98 n/a 96-97 n/a n/a
CKF Sensor (Crankshaft Speed Fluctuation)
defective circuit or unplugged / defective sensor
58- Accord Civic CRV CRX Del Sol Odyssey Prelude
98 * n/a n/a n/a n/a n/a n/a
TDC Sensor 2 (Top Dead Center)
defective circuit or unplugged / defective sensor
* with V-6 engine only
61- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Oxygen Sensor, Heated - Sensor 1 (Primary)
high voltage, low voltage, or slow response
63- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Oxygen Sensor, Heated - Sensor 2 (Secondary)
high voltage, low voltage, or slow response
65- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Oxygen Sensor Heater (Secondary)
malfunctioning or defective oxygen sensor heater
67- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Catalyst system Efficiency Below Threshold
malfunctioning or defective catalyst system
70- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a n/a 96-98 96-98
Automatic Transmission
malfunction with the automatic transmission controls
71- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Cylinder 1 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire
72- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Cylinder 2 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire
73- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Cylinder 3 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire
74- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Cylinder 4 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire
75- Accord Civic CRV CRX Del Sol Odyssey Prelude
98 * n/a n/a n/a n/a n/a n/a
Cylinder 5 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire
* valid code for V-6 engine only
76- Accord Civic CRV CRX Del Sol Odyssey Prelude
98 * n/a n/a n/a n/a n/a n/a
Cylinder 6 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire
* valid code for V-6 engine only
80- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 n/a n/a n/a 96-98 96-98
Exhaust Gas Recirculation
insufficient flow detected
86- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
ECT Sensor (Engine Coolant Temperature)
circuit range / performance problem
90- Accord Civic CRV CRX Del Sol Odyssey Prelude
97-98 96-98 n/a n/a n/a 98 97-98
Evaporative Emission Control System
leak detected in the fuel tank area
91- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 n/a n/a n/a 98 97-98
Fuel Tank Pressure Sensor
low input
92- Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-97 96-98
Evaporative Emission Control System
insufficient purge flow
----------------++++++++++++++++++++++++++++++------------------------------
85-87 obd0 ecu error codes
LED display Symptom - Possible Cause for 1985 through 1987 Honda Vehicles
Note: OOOO all 4 lamps on, XXXX all 4 lamps off
OOOO Engine will not start - Check for disconnected control unit ground connector. Also check for a loose connection at the ECU main relay resistor. Possible faulty ECU.
OOOO Engine will not start - Check for a short circuit in the combination meter or warning light wire. Also check for a disconnected control unit ground wire. Possible faulty ECU.
OOOX System does not operate - Faulty ECU
OOXO System does not operate - Faulty ECU
OOXX Fuel-fouled spark plugs, engine stalls frequently - Check for a disconnected MAP sensor coupler or an open circuit in the MAP sensor wire. Also faulty MAP sensor.
OXOO System does not operate - Faulty ECU.
OXOX Hesitation, fuel-fouled spark plugs or engine stalls frequently - Check for disconnected MAP sensor vacuum hose.
OXXO High idle speed during warm-up, continued high or hard starting at low temperature - Check for disconnected coolant temperature sensor connector or an open circuit in the coolant temperature sensor wire. Also faulty Coolant Temperature sensor.
OXXX Poor engine response when opening the throttle rapidly, high idle speed or engine does not rev-up when cold - Check for a disconnected throttle angle sensor connector. Also check for an open circuit in the throttle angle sensor wire. Also faulty throttle angle sensor.
XOOO Engine dose not rev-up, high idle speed or erratic idling - Check for a short or open in the crank angle sensor wire. Spark plug wires interfering with the crank angle sensor wire. Also faulty crank angle sensor.
XOOX Same as above (XOOO)
XOXO High idle speed or erratic idling when very cold - Check for disconnected intake air temperature sensor or an open circuit in the intake air temperature sensor wire. Also faulty Intake Air Temperature sensor.
XOXX Continued high idle speed - Check for a disconnected idle mixture adjuster sensor coupler or an open circuit in the idle mixture adjuster sensor wire. Also faulty Idle Mixture Adjuster sensor.
XXOO System does not operate at all - Faulty ECU
XXOX Poor acceleration at high altitude when cold - Check for a disconnected atmospheric pressure sensor coupler or an open circuit in the atmospheric pressure sensor wire. Also faulty Atmospheric Pressure Sensor.
XXXO System does not operate at all - Faulty ECU
XXXX Same as above (XXXO)
CODE PROBABLE CAUSE for Honda Vehicles 1988 and later.
0 Faulty ECU (no signal)
1 Oxygen sensor or circuit.
2 Faulty ECU
3 & 5 Manifold Absolute Pressure (MAP) sensor or circuit.
4 Crank angle sensor or circuit
6 Coolant temperature sensor or circuit
7 Throttle angle sensor or circuit.
8 TDC position/crank angle sensor or circuit.
9 Crank angle sensor or circuit
10 Intake air temperature sensor or circuit.
11 No particular symptom shown or system does not operate - faulty ECU
12 Exhaust gas recirculation (EGR) failure
13 Atmospheric pressure sensor circuit.
14 Electronic air control valve (EACV)
15 No ignition output signal - possible faulty igniter.
16 Fuel injector circuit.
17 Vehicle speed sensor or circuit (VSS)
19 Lock-up control solenoid valve (automatic transmission)
20 Electronic load detector - possible open or grounded circuit in ECU wiring.
21 VTEC spool solenoid valve circuit (Civic & Del-Sol)
22 VTEC oil pressure switch circuit (Civic & Del-Sol)
23 Knock sensor (Prelude)
30 A/T control unit ECM fuel injection signal "A" (Accord & Prelude)
31 A/T control unit ECM fuel injection signal "B" (Accord & Prelude)
41 Heated oxygen sensor - heater circuit.
43 Fuel supply system circuit (except D15Z1 engine)
45 Fuel system out of range - rich or lean
48 Heated oxygen sensor circuit (D15Z1 engine)
50 Mass airflow sensor.
61 Front oxygen sensor response slow.
63 Rear oxygen sensor circuit voltage out of range.
65 Rear oxygen sensor circuit malfunction.
67 Catalytic converter efficiency low.
70 Automatic Transaxle problem.
71 through 76 Cylinder misfires
80 Insufficient EGR flow
86 Engine coolant temperature sensor circuit.
92 Evaporative emission purge valve problem
*Please only use this as a guide* As some are different. This should only be used as a starting point.