Quote:
Originally Posted by 1993CivicVX
Heh, cool. So it's the Lean Air Fuel Sensor. Is that part of the o2 sensor?
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That page needs a slight correction... LAF = Linear Air Fuel sensor, not Lean. The 5-wire O2 sensor IS the Linear Air Fuel sensor, not just part of it.
The Helm's manual (Helm, Inc. reprints the Honda workshop manuals) pretty much says to reset the ECU (I'll get to that in a sec) and turn the ignition on. If the CEL comes on immediately with a code 48, check for shorts or breaks in the wiring. If no code comes up, take the car for a test drive. If the code pops up again during the drive, check for breaks in the wiring between the sensor and ECU. If the wiring checks out, replace the sensor.
Resetting the ECU is pretty easy... Switch the ignition off, pop the hood and take a look at the fuse box under there. Remove the fuse for the hazard lights (aka 4-way flashers) from it's socket for 5 seconds and then plug it back in. Done. Close things up and go for a drive.
Checking wiring can be kinda confusing. Actually doing the checks is easy, but figuring out exactly which wire you're supposed to be checking can be tough. You need a multi-meter with a continuity check function and long (long enough to reach from the passenger footwell to the LAF electrical connector) test leads.
Looking at the wiring harness side of the LAF connector, you'll see 7 wires. As I understand it, two of those wires connect to a calibration resistor in the
sensor's side of the connector... That's why you only see 5 actually running down to the sensor itself. Anyway, those 7 wires run back to 7 terminals in the ECU electrical connectors.
A little preparation... You'll have to unbolt the ECU from the side of the passenger's foot well to reach it's electrical connectors. You can probably get away with just leaving the ignition off while testing, but if you want to be extra safe, disconnect the negative battery terminal.
Ok, actual testing: You're going to disconnect the LAF and ECU connectors and then touch one multimeter test lead to the appropriate terminal of each to make sure the length of wire between the two isn't broken. The meter should beep if the connection is good.
If the wire checks out, it's a good idea to then do a similar test between one of those terminals (it doesn't matter which - they're connected, right?) and body ground. That simply checks that the wire isn't shorted out somewhere.
Body ground is simply the car body. The body is made of steel, which is conductive. The negative terminal of the battery is connected to the body as well, so body ground is simply an easy return path to the battery for most of the car's electrical components... Like a giant wire. Anything conductive (metal) that's directly bolted to the body or engine (including most solid black wires - NOT black with a colored stripe - you'll find around the car) is therefore connected to the battery's negative terminal.
If you want to use some random metal object as a ground connection, make sure it isn't painted. Paint is generally non-conductive, so you won't get a connection to ground by simply touching the meter probe to the paint.
Back to testing: The ECU connectors are each assigned a letter. The pins in each of those connectors are then numbered. Connector A is the largest with 26 pins - 2 rows of 13. Before you unplug the connectors from the ECU, orient it so connector A is on your left. The pins are numbered top to bottom, progressing to the right. That is, the top left-most pin is #1, the pin immediately under it is #2, the pin to the right of 1 is #3, the pin under 3 is #4, to the right of 3 is #5, #6 is below 5 and so on. So you'll have all the odd numbered pins in the top row, and the evens in the bottom row. Some pins are a slightly different size than the others, but it shouldn't be enough to upset the numbering scheme. Some positions in the connectors will be empty - there won't be a pin or wire there, but one could be plugged in... Don't skip them. Count the empty positions as if there were a wire there.
To the right of Connector A is Connector B. It's the smallest with two rows of 8 pins, 16 in all. Connector C is skipped in most Civics for some reason... I guess they didn't need the wiring capacity. So that leaves the right-most connector - D. D should have two rows of 11 pins, 22 in all.
If you look closely at the ECU connectors, they should have a molded-in cover snapped down over the rows of pins. If you release that cover (it's got a little snap-clip thing at each end), you can touch each pin from the wire side, known as back-probing.
And now for the actual work. Oh, wires are identified by their color... The color of the wire's insulation (the casing around the bare wire) followed by the color of the stripe on the casing, if it has one. The first wire - yel/blk is yellow with a black stripe.
I'm going to list these as the color of the wire at the LAF connector, followed by the ECU pin. The colors may be the same at the ECU, but some color combinations are re-used, and sometimes the colors change going from one wiring harness to the next, so it's better to figure it out by the pin number and just consider it confirmation if the color combination is the same at the ECU.
yel/blk to pin A6
blk to pin A23
wht to pin D3
wht/blu to pin D8
orn/blu to pin D14
orn to pin D16
grn/wht to pin D22
Happy wire prodding.
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The white plastic piece is not the silicon boot of the o2 sensor is it?
Linear Mode
