The longer I drive this thing the curiouser it gets. The 2.6 w/five speed has a mechanical speedometer cable and of course an O2 sensor. I've had this ongoing problem of the check engine light flashing which always reads out a code 13 for a bad O2 sensor. I figure fine, it hasn't affected performance I'll replace it when it's time for inspection. After fifteen years and 432,000 miles the speedometer cable breaks (nothing lasts anymore). That doesn't bother me much either because I know how fast I drive (slower than everyone else) and I can pretty much tell how fast I'm going by the sound of the engine and gear that I'm in. What does bother me is for the next two weeks I drive and the check engine light doesn't flash; not once. Week three I replace the busted cable and within four miles the check engine light starts flashing again?! No wires were removed or disconnected and the cable housing stayed in place while I waited for the delivery of the replacement. Any clues as to why a working speedometer would affect the check engine circuit? Speedometer's pretty worn. Squalls like an angry groundhog on cold days and the needle shoots up to the max until it get's warmed up, but what's the circuit connection?

There is nothing electrical tied in with your mechanical speedometer. I could be wrong, but I'm pretty sure these engines didn't use speed sensors for any type of engine management decisions.

Code 13 indicates a fault in the oxygen sensor circuit. It does not mean, "just replace the sensor". It means the circuit is open, or the values the computer is recieving are out of acceptable ranges.

You could change your 02 sensor but that might not be the problem, run a quick diagnostic first -- it only takes a few minutes. I orget the exact procedure but it involves a digital multimeter.

"There is nothing electrical tied in with your mechanical speedometer"

That's what logic tells me, but then I'm stuck with the fact that while the speedometer was out of commission, no fault was displayed. Within minutes of the speedometer's repair the fault shows up again. It's a curiosity more than a problem. I posted the problem with the "13" code before. At certain engine speeds the check engine light comes on. If I let off the gas pedal it goes out. If I tromp on the gas pedal it goes out.
And when the code is read it is always "13". The sensor is less than a year old, it wasn't wire rigged (exact replacement). I've traced the wire and there's no apparent break or current leakage. This business with the speedometer is the first clue that it might not be the sensor itself.
I just can't connect the dots to figure out why one would affect the other.

There is some connection in the cluster somehow, as indicated by the )2 sensor light that cycles between posts every 90,000 miles. Dunno what, dunno where, but it is in there.

Randii

It sounds stupid, but is it plugged in securely. Your symptoms are exactly what occurs if you unplug the O2 sensor.

Michael

earlier this evening I linked to a thread from a few years back about 2.6 idle issues & an explicit nugget from Mr. Marcucci jumped out at me regarding this:


thread

Isuzu refers to it as the CSS - Car Speed Sensor. if the sensor itself was conking out it would possibly throw a code 63. you can check it at the connector behind the speedo & it should alternately indicate continuity & open circuit as the cable rotates(4 pulses/rev).

by chance have you ever gotten a code 44 over the course of your o2 problem?

Leave it to Isuzu, man I think that means I have to fix MY speedo. Wonder if there's also this function on the 3.1....

Not just Isuzu. Pretty common on nearly all vehicles since around 1990. The old work truck that I drive ('92 F250) has a very similar setup. Besides the symptoms described above, the VSS is integral to the control of the shift points on automatic trannies.

It's the stupid things that alway get me, so I make a point of checking the stupid things first thinking as stupid as I can. The plug is secure in the socket and I blew it out with contact cleaner for good measure, but I'm about ready to cut into the wiring harness to see if I can tease out the wire and find something wrong with it. I know driving these salty northeast roads did a number on my fuel tank wires. Maybe some crack in the insulation has done the same to the O2 wire.

No code 44. Code 13 everytime. I thought about the decelleration but I figured the throttle position switch was the circuit path for the ECU. I know from experience if the TPS is messed with, there are major changes in engine operations. In this case with the speedometer on the disabled list there was no change in engine operation at all with the added benefit of no blinking "check engine" light. It's gotta be something with the connector or the wire if not the O2 sensor itself. I'm sure the speedo has some "close circuit" function for the display because sitting in the driveway in neutral I can't get the check engine light to blink no matter what rpm I'm revving. It's only in motion that it happens and now I know it's only in motion with working speedometer...
so close....