How to get Prelude CEL codes and what they mean

(Thanks to Schwarzpm)


Get a paperclip and bend it into a U shape.
Make sure the engine’s off and look behind the centre console near the clutch pedal for the service connector; it’s a little (normally) blue connector with 2 wires attached.
Insert the paperclip into the connector to short the 2 wires.
Now turn on the ignition but don’t start the engine, so the dash warning lights light up.
If the CEL light on the dash stays on permanently there are no CEL problems.
If it starts to flash you’ll need to make a note of how many flashes there are.
The CEL light will flash in a loop if there is more than 1 problem

Short flashes mean 1
Long flashes mean 10




NB. There were 2 sets of ODB1 error codes in the tech section 03/12/2006 - They each have slight differences so have included both lists below....




What your fault codes really mean in english
(link submitted by 2Lude)

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Here is the list of codes taken from the Honda Workshop Manual

0 Engine Control Module (ECM)
1 Heated Oxygen Sensor (HO2S)
3 Manifold Absolute Pressure (MAP SENSOR)
4 Crankshaft Position (CKP SENSOR)
5 Same as above
6 Engine Coolant Temperature (ECT SENSOR)
7 Throttle Position (TP SENSOR)
8 Top Dead Centre Position (TDC SENSOR)
9 No. 1 Cylinder Position (CYP SENSOR)
10 Intake Air Temperature (IAT SENSOR)
12 Exhaust Gas Recirculation (EGR VALVE LIFT SENSOR)
13 Barometric Pressure (BARO SENSOR)
14 Idle Air Control (IAC VALVE)
15 Ignition Output Signal
16 Fuel Injector
17 Vehicle Speed Sensor (VSS)
20 Electric Load Detector (ELD)
21 Variable Valve Timing & Valve Lift Electronic Control (VTEC) Solenoid Valve
22 Variable Valve Timing & Valve Lift Electronic Control (VTEC) Pressure Switch
23 Knock Sensor (KS)
41 Heated Oxygen Sensor (HO2S) Heater
43 Fuel Supply System





obd1 check engine codes

Thanks to RocketPantsBob.


1 O2A - Oxygen sensor #1
2 O2B - Oxygen sensor #2
3 MAP - manifold absolute pressure sensor
4 CKP - crank position sensor
5 MAP - manifold absolute pressure sensor
6 ECT - water temperature sensor
7 TPS - throttle position sensor
8 TDC - top dead centre sensor
9 CYP - cylinder sensor
10 IAT - intake air temperature sensor
12 EGR - exhaust gas recirculation lift valve
13 BARO - atmospheric pressure sensor
14 IAC (EACV) - idle air control valve
15 Ignition output signal
16 Fuel injectors
17 VSS - speed sensor
19 Automatic transmission lockup control valve
20 Electrical load detector
21 VTEC spool solenoid valve
22 VTEC pressure valve
23 Knock sensor
30 Automatic transmission A signal
31 Automatic transmission B signal
36 traction control found on JDM ecu's
41 Primary oxygen sensor heater
43 Fuel supply system
45 Fuel system too rich or lean
48 LAF - lean air fuel sensor
54 CKF - crank fluctuation sensor
58 TDC sensor #2
61 Primary oxygen sensor
63 Secondary oxygen sensor
65 Secondary oxygen sensor heater
71 random misfire cylinder 1
72 random misfire cylinder 2
73 random misfire cylinder 3
74 random misfire cylinder 4
80 Exhaust Gas Recirculation insufficient flow detected
86 ECT Sensor (Engine Coolant Temperature) circuit range / performance problem
90 Evaporative Emission Control System leak detected in the fuel tank area
91 Fuel Tank Pressure Sensor low input
92 Evaporative Emission Control System insufficient purge flow

Honda ECU List

RocketPantsBob

PG6 : 88-89 Integra (all makes)
PM5 : 88-91 Civic/CRX DX
PM6 : 88-91 Civic/CRX SOHC Si
PM7 : 89-91 DOHC ZC (JDM 'EF' ECU)
PM8 : 88-91 CRX HF
PM9 : 88-91 Civic STD
PR2 : 89-91 ZC (Euro)
PR3 : 89-91 JDM B16A EF8/9
PR3 -J00 or J51 : 92 JDM Integra B16A EF8/9
PW0 : 89-91 JDM B16A EF8/9 DA6-XSi
PR4 : 90-91 Integra LS/GS
PS9 : 88-91 4 door Civic EX Auto
P05 : 92-95 OBD-1 Civic CX
P06 : 92-95 OBD-1 Civic DX
P07 : 92-95 OBD-1 Civic VX
P08 : 92-95 OBD-1 Civic D15 JDM
P0A : 94-95 OBD-1 Accord EX
P13 : 93-95 OBD-1 Prelude Vtec
P14 : 93-95 OBD-1 Prelude Si (non Vtec)
P27 : 92-95 OBD-1 EG JDM Civic 1600 sohc
P28 : 92-95 OBD-1 Civic Si/Ex
P30 : 92-95 OBD-1 DelSol DOHC Vtec Si/EG SiR
P54-G31 : 1997 Honda Accord 1.8 LS
P61 : 92-93 OBD-1 Integra GSR
P72 : 94-95 OBD-1 Integra GSR
P72 : 96-00 OBD-2 Integra GSR
P73 : 96-00 OBD-2 Integra Type-R (JDM & USDM)
P74/75: 92-95 OBD-1 Integra LS/GS
P75 : 96-00 OBD-2 Integra LS/GS
P2N : 96+ OBD-2 Civic HX Coupe
P2P : 96+ OBD-2 Civic EX Coupe
P2E : 96+ OBD-2 Civic DX Coupe
P2M : 96+ OBD-2 NZ Civic SOHC VTEC
P2T : 99+ OBD-? Civic Si Coupe
P5P : 97-00 OBD-2 Prelude Type-S (JDM ECU)
PBA : 97+ US Acura 1.6EL
PCT : 98+ JDM ITR / CTR
PCX : 99+ OBD-? S2000

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Apexi VAFC Tuning

Best write up and explanation I have seen in a long time...mostly references to the S2000, but it gives you a explanation to how the unit works.

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please note, you still need to use a RR preferably with a wide band O2 sensor as noted in the above thread.

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O2 sensor

Originally called a "Lambda sensor", the oxygen sensor monitors the level of oxygen (O2) in the exhaust so the ECU can regulate the air/fuel mixture to reduce emissions.

The sensor is mounted on the exhaust manifold, next to the flexi and generates a voltage signal proportional to the amount of oxygen in the exhaust.

As time goes on, contaminants from normal combustion accumulate on the element, reducing the sensor's ability to respond quickly to changes in the air/fuel mixture. The sensor's output voltage may not be as high as it once was, giving the false impression that the air/fuel mixture is leaner than it actually is. The result can be a richer-than-normal air/fuel mixture that causes fuel consumption and emissions to rise.

Approximately after 60-70% throttle, the ECU stops trying to be ECO friendly and will use as much fuel as the map sensor tells it to use.

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Map sensor

You have two ways the ecu works; closed loop (ecu reads from o2 sensor) and open loop (No O2 feedback). When in closed loop (normal driving) your ecu takes readings from your o2 sensor to adjust for better mpg and daily driving.

When you accelerate the map sensor is sending a voltage reading to the ecu telling it how much pressure is coming into the intake manifold. The map sensor on a stock honda which reads between 0-5Volts.

The ECU takes this reading and cross references it against a table (fuel map) and tells the injectors how much fuel to use (and for how long - duty cycle?)

Manipulating the map sensor signal

By using a VAFC (or similar on a stock ECU), you can manipulate the voltage of the air correction signal which in return changes fuel.

The only thing you can truly tune with a VAFC is vtec engagement and Open Loop (WOT) tuning. Partial throttle tuning is worthless as the o2 sensor will send a signal back trying to compensate to get back to a stock (14.7:1 A/F) reading.

But when in Open Loop or Wide open throttle your ecu reads straight from the map sensor and uses pre-programmed maps from Honda built into the ecu to run the car.

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Wide Band O2 sensor - AFR (air fuel ratio)

We have already discussed the basics of what an O2 sensor does (I hope).

AFR (air fuel ration)

The exhaust gases are made up of air and waste fuel. This is measured as a ratio eg 14 parts air to 1 part fuel. The ECO friendly/efficient burn ratio of fuel to air is around 14.64:1.

This ratio of 14.64 is called the stoichiometric point, and this is where all the available oxygen has combined with all the available fuel leaving no free residual oxygen (keeping green piece happy, however they'll find something else to moan about ).

The stoichiometric point, is also referred to as the Lambda point, where Lambda=1, any measurement above or below 1 is rich or lean

OEM Narrow band sensor

A typical car setup will not vary much from 14.64 (the ECU will alter fuelling to prevent it running too rich/lean). For this reason an OEM O2 sensor really only needs to measure say from 14:1 to 15:1 for example. As soon as the outer limits are met the ECU will compensate fuel, returning the emittions to close to the stoichiometric point.

These 'narrow band' sensors are accurate in the region surrounding stoichiometric operation and leaner. Unfortunately, in the rich region where high performance engines usually operate, their accuracy and repeatability is virtually non-existent.

Wide band O2 sensor

This type of sensor is commonly referred to as “laboratory grade” and works on a different principle than the normal oxygen sensor you would find in your car. Its design makes precision AFR measurement possible over the entire operating range, from a ration of 10:1 (very rich) to 20:1 (very lean)

A typical WB sensor will return a voltage as per the following table.

Code:

Vout    Lambda    AFR     1.40    0.686    10.08     1.45    0.696    10.23     1.50    0.706    10.38     1.55    0.716    10.53     1.60    0.727    10.69 1.65    0.739    10.86     1.70    0.750    11.03 1.75    0.762    11.20     1.80    0.774    11.38     1.85    0.787    11.57     1.90    0.800    11.76     1.95    0.814    11.96     2.00    0.828    12.17     2.05    0.842    12.38     2.10    0.857    12.60     2.15    0.873    12.83     2.20    0.889    13.07      RICH - ideal for N/A tuning 2.25    0.905    13.31       RICH - ideal for N/A tuning 2.30    0.923    13.57      RICH - ideal for N/A tuning 2.35    0.941    13.84     2.40    0.960    14.11 2.45    0.980    14.40     2.50    1.000    14.70      stoichiometric point / Lambda =1 2.55    1.037    15.25     2.60    1.078    15.84     2.65    1.121    16.48     2.70    1.169    17.18     2.75    1.220    17.93     2.80    1.276    18.76     2.85    1.337    19.66     2.90    1.405    20.66 4.00    (free air)

The voltage can be converted and displayed on a guage such as





But that doesn't really help you tune your engine. You need to log the results against other factors such as RPM, producing a graph showing at what rev ranges you should increase/decrease fueling.

This is the best example I could find of an AFR graph, showing before and after tuning. I believe it to be from a BMW ( but the principle in the same). It is stock tuned to be lean (15.5:1) in the low and mid range RPM, running richer (12.5:1) in the high RPM's.



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Knock Sensor

Knock sensors are typically only found on JDM engines (for preludes anyway).

A knock sensors is basically a microphone and plays 2 roles in the engine:-
1) monitor engine operation to optimize performance (and saving fuel in the process)
2) protect the engine against power-robbing and potentially destructive engine knock.

How is knock caused?

Knock occurs when the air-fuel mixture doesn’t burn smoothly or is ignited too soon.

1) Knock can be caused by “hot spots” in the cylinder, such as carbon deposits or spark plugs that are too hot for the engine, sharp edges on the piston top, or high combustion chamber temperatures. These hot spots ignite the air-fuel mixture before the spark plug fires.

2) Knocking also occurs if spark timing is advanced too far and the spark occurs while the piston is too far before TDC, causing a collision between the rapidly expanding gases from combustion and the top of the piston as it moves up the cylinder wall.

3) Some engines are prone to knocking. The engines that are likely to knock are usually high performance and poorly maintained. Both situations require the engine to continually operate at the edge of knocking.

4) Using petrol with a low octane rating can cause knocking.

5) Anything that increases combustion chamber temperature can cause knocking such as failure of the EGR, a cooling system problem, burning engine oil, or incorrect spark plug heat range.

6) On an older vehicle, especially one used primarily for stop-and-go driving, deposits can build up in the combustion chamber leading to the hot spots that cause knocking.

How does the ECU use the knock sensor?

The knock sensors sends a base or “no knocking” reference signal to the ECU. If knocking occurs, the sensor detects the increased vibration and increases its signal to the ECU. The ECU then slightly retards timing until the sensor signal returns to the reference level.

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Distrubutor (Dizzy) Timing Chat

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P13 pinout

Thanks to bigrichy.



Contact Color Description
A1 brn Injector #1
A2 yel Injector #4
A3 red1 Injector #2
A4 grn/yel VTEC Solenoid Valve
A5 blu Injector #3
A6 or/wht HO2S heater coil
A7 grn/blk1 PGM-FI Main Relay coil
A8 grn/blk2 Shorted to A7
A9 blk/blu IAC Valve
A10 - -
A11 red2 EGR Control Solenoid
A12 blu/red Condenser Fan Relay
A13 blu/wht MIL
A14 - -
A15 red/blu A/C Clutch Relay
A16 wht/grn Alternator
A17 pink IAB Solenoid Valve
A18 - -
A19 wht Intake Control Solenoid Valve
A20 red/grn EVAP Purge Control Solenoid
A21 yel/grn1 ICM
A22 yel/grn2 Shorted to A21
A23 blk1 GND
A24 blk2 GND
A25 yel/blk PGM-FI Main Relay (power)
A26 blk/red VTEC Pressure Switch (GND)
B1 yel/blk PGM-FI Main Relay (power)
B2 brn/blk GND
B3 - -
B4 - -
B5 blu/blk To A/C Switch
B6 - -
B7 - -
B8 red/grn PSP Switch
B9 blu/red Starter Cut Relay
B10 orn2 VSS
B11 orn3 CYP
B12 wht CYP
B13 orn/blu TDC
B14 wht/blu TDC
B15 blu/grn CKP
B16 blu/yel CKP D1 wht/yel Battery
D2 grn/wht1 Brake Switch
D3 red/blu KS
D4 brn/wht SCS
D5 - -
D6 lt blu or lt grn VTEC Pressure Switch
D7 lt grn/red Data Link Connector
D8 - -
D9 wht/red ALT
D10 grn/blk ELD
D11 red/blk TP Sensor
D12 wht/blk EGR Valve Lift Sensor
D13 yel/blu ECT Sensor
D14 wht HO2S Sense
D15 red/yel IAT Sensor
D16 - -
D17 wht/blu MAP Sensor
D18 - -
D19 red/wht EGR Valve Lift Sensor
D20 yel/wht TP Sensor
D21 blu/wht MAP Sensor
D22 grn/wht2 TP Sensor

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Replacement of O2 / Lambda sensor

Thanks to Don Paulos

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Installing VSS Converter (KPH to MPH)

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