this information is strait from the ECM/PCM ASE L-1 engine information sheets. i belive this info will help you diagnose your own cars and learn what to look for when diagnosing sensors. these psi, voltage, amps, ohms, ect... readings ARE NOT exact for your vehicle but it gives you something to go off of. please make sure you know what kind of readings you should expect when testing. but most important is that you know how to test sensors to aid in your diagnosis.

fuel system:
avg 50 psi. min of 45 and should hold up to 2 min after engine is shut off

ignition system
firing order: 1,3,4,2
avg 1,200 omhs per foot in plug wires
PCM can use crank and/or cam timing for adjustments
control module is PCM controlled

Idle speed
750-850 rpm with idle air control valve (IAC) value of 15% to 25%

Clear flood mode
when throttle is is at wide open throttle (80% and higher) and engine speed is below 400 rpm, the pcm shuts off the fuel injectors

Run mode: open and closed loop
Open Loop: when engine is running above 400 rpm on cold start, the pcm does not use oxygen sensor signal. it calculates fuel injector pulse width from the throttle position sensor, intake air temp, mass air flow, and crank sensor. it will remain in open loop untill the following conditions are met:
both O2 sensors are sending varying signals to PCM
ECT above 150 degrees F
one minute has elapsed since start up
TP of less than 80%
Closed Loop: when the conditions are met, it enters closed loop. this means the PCM adjust fuel injector pulse width based on O2 sensor voltage inputs. below .45 V causes the PCM to increase the injector width in response to lean mixture. and above .45 V it reduces the width in response to a rich mixture.

Acceleration Enrichment Mode
during acceleration, the PCM uses mass airflow and rate of change in throttle position to calculate fuel injector pulse width. at WOT the control system enters open loop operation.

Sorry everyone, i have completely forgoten about this topic. im here to finaly try to finish it.
This next section is about testing your sensors and what kind of readings you should get.

Mass Airflow (MAF) sensor
This senses the airflow into the manifold. the reading can vary from .2v at key on, engine off, to 4.8v at max airflow. at sea level with no load, the reading should be .7v.

Manifold Absolute Pressure (MAP) sensor
senses the intake manifold absolute pressure. the MAP is used by the PCM for OBD2 diagnostics only. The sensor reading may very from 4.5v in 0 in. hg (key on, engine off, sea level) to .5v at 24 in. hg. At sea level with no load idle with 18 in. hg, the reading will be 1.5v.

Trottle Position (TP) Sensor
This sensor is a 3-wire potentiometer. the reading varys from .5v at closed throttle to 4.5v at WOT. the PCM inteprets that the throttle opening more than 80% is WOT, at 80% it should read about 3.7v.

Engine Coolant Temperature (ECT) Sensor
this is a negative temperatrue coefficient thermistor that senses the engine coolant temp. the sensor can range from -40 to 248 F. At 212 degrees the sensor should read .5v.

Intake Air Temperture (IAT) Sensor
this is a negative temperatrue coefficient thermistor that senses the engine coolant temp. the sensor can range from -40 to 248 F. At 86 degrees the sensor should read 2.6v.

Heated Oxygen Sensors
Sensor 1/1 is located on the Bank one exhaust (cylinders 1,3,5 on V6 and all cylinders for inline 4) and is the upstream sensor that is used for closed loop fuel control and OBD2 monitoring. Sensor 1/2 is located after the catalytic converter (downstream). Its signal is used for monitoring of the Catalytic Converter. The sensor can vary from 0v - to 1v. when a sensor is reading less than .5v the oxygen content around the sensor is high. When it reads more than .5v oxygen content around the sensor is low. With the key on engine off the sensor will read 0v.

A/C pressure sensor
This a 3-wire solid state sensor for the A/C high side. The reading can vary from .25v at 25 psi to 4.5v at 450 psi. this signal is used by the PCM to control the compressor clutch, radiator fan, and adjust the idle airflow to compensate for the added engine load from the compressor. The PCM will also disengage the compressor if the pressure is below 40 psi or above 420 psi.

Fuel Level Sensor
this is a potentiometer that determines the fuel level. the reading will vary from .5v at 0% fuel level and 4.5v at full tank. 1/4 level will read 1.5v and 3/4 will read 3.5v.

Fuel Tank Pressure Sensor (EVAP)
senses vapor pressure or vacuum in the EVAP system compared to atmospheric pressure. the reading can vary from .5v at .5 psi (14in. H2O) vacuum to 4.5v at .5 psi. With no pressure of vacuum (gas cap off) it will read 2.5v.

 

ACTUATORS
Fuel pump relay
when energized it supplies battery voltage to fuel pump. The coil relay spec is 48 -+6 ohms

Fan Control relay
When energized supplies battery voltage to the radiator/condenser fan. The PCM will turn on the fan when the ECT reaches 210 degrees and off when it drops below 195 degrees. it also runs when compressor clutch is engaged. coil resistance is 48 +- 6 ohms.

A/C Clutch Realy
energizes compressor clutch. coil reading should be 48+-6 ohms

Idle Air Control Valve (IACV)
A stepper motor that regulates the amount of air to by-pass the throttle plate. used to control idle speed during closed throttle operation. A 0% indicates a PCM to fully closed command to the air passage and 100% is a fully open air passage.

Exhaust Gas Recirculation (EGR) Valve control solenoid
A duty cycled controlled solenoid that, when energized, supplies manifold vacuum to a diagphram type EGR valve. When its not energized, the vacuum supply is blocked and the valve chamber is vented to close the valve. The PCM controls the duty cycle of the EGR, 0% is fully closed, 100% is fully open. EGR is used during steady cruising. solenoid wire resistance is 48+-6 ohms

Fuel Injectors
each injector is energized once per revolution timed on the intake stroke. the resistance of the injector spec is 12+-4 ohms.

EVAP Purge Control Solenoid
A duty cycled solenoid that controls the flow of gas vapors to the intake manifold. the solenoid is enabled when ECT reaches 150 degrees and throttle is not closed. 0% is closed flow and 100% is completely open flow. winding spec should measure 48+-6ohms

I hope this info will help you on your diagnosis and please let me know if there is anything i need to add of edit. GL all!!!
Modified by SOHC_4dr at 10:48 AM 10/30/2008

 

Here is more info on the operation of most of these sensors. Hope this helps you even more!

http://www.aa1car.com/library/1999/cm69910.htm

 

anyone find this helpfull? i hate for it to be for nothing

 

interesting read. should be put in a FAQ somewhere..

 

hmm i somewhat remember this from taking the test.. good post. should help some people who like to read rather than just type and ask questions without searching.

some of the ohm readings are a little off but other than that its good. but then again, it isnt just for hondas lol.

somewhere in there, should be a section for air fuel sensors. not just the old 0-1v, and no im not talking about a wideband, nessacairly

 

it took me a while to understand the diff between the air fuel sensors and O2 sensors. i'll try to get the info together and post it up sometime. im a bit dyslexic so i have a hard time readinbg the diff between them and remembering it lol

 

lol ahha.. its all good.but now that honda and most auto manu. are using air/fuel sensors and not the old non-linear sensors.

 

anyone else find this helpfull?

 

good stuff to have!! good work!

 

gettin lots of veiws. thats good

 

do you have a wiring diagram of the IACV for an OBD2A (96-98) DX hatchy??? I have looked at numerous diagrams and its starts off with three wires and then goes into two wires somewhere so i am just want to see the whole diagram thanks...

 

^ PM'd you

 

Strange post, since i just got the ASE study guides for L1 in the mail and was just reading the reference book with all the sensors in it

 

i've had the info for over a year. it's just i never thought to put it up untill i got tired of people askin what sensor is suppose to do what or what reading, ect...

 

Air Fuel sensor? how does it operate differently compared to oxygen sensor?

how can it be tested? sorry for the newb question.

just trying to understand.

 

Incase anyone is wondering, If you go onto the ASE website they will send you a complete study guide for all the tests for free

 

An air/fuel guage? like an aftermarket one your talking about?

They just tap into the O2 Sensor and show what the O2 sensor is reading thats all

 

so let's say if i were to diagnose a suspected "A/F sensor" failure, can i just pinch the signal wire using a snap-on modis for example, and test it like a H02S?
should i expect to see pretty much the same signal output like a regular H02S?
TIA.

 

no hes not meaning a guage to see the ratio. he's meaning a sensor that is similar to the O2 sensor.

here is a link to the Lean Burn opperation which uses the air fuel sensors in stead of O2 sensors. the diff really is the readings and name. http://www.insightcentral.net/encyclopedia/enlaf.html