Mazda Tribute This low-priced SUV allows the driver the versatility of an SUV without the big fuel bill of many of the vehicles in the SUV class.

OBD2 troubleshooting

Old 06-30-2019, 06:36 PM
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Default OBD2 troubleshooting

SO I bought an 03 tribute for $750, Figured id get some repairs in and have a nice ES for less. No major mechanical issues and I have been replacing standard overhaul stuff, brakes, plugs, coils ETC, with all the work the bulk of the noise and roughness is gone. The engine idle is now stable with no surging unless the AC is on.

I ran into an issue with the OBD2 port not connecting, got out my multimeter and checked the voltages, fuse is intact, no shorts but the ECU pin 2 and 10 voltages weren't in spec so I replaced the ECU. Still having the same problem, tested with 3 different OBD readers. ended up modifying some pinout jumpers to test if it was just a bad DLC but no dice. voltages at the OBD reads I have with modified jumpers are in spec, no shorts and still no communication.

Found a video by Scotty Kilmer and started pulling various sensors at random with no improvement. I have torque and car scanner set to SAE j1850 PWM based on the DLC pinout to decrease time and increase retries.. Considering I have changed the ECU, bypassed the DLC, have proper voltages I'm assuming a sensor is out but I'm not sure which one. I think I got most in the main engine compartment, the only ones I'm not seeing are the O2 sensors and some others near the lower engine but I'll wait for it to cool.

I'm essentially throwing darts blindfolded in the dark on a spinning merry go round and am trying to improve my odds.

Here are the engine symptoms,
Engine runs rich
Flashing CEL
No communication
small amount of idle vibration could be from a broken transmission mount
Old 07-01-2019, 03:38 AM
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Does your scanner work with another Escape of the same vintage? Early OBD2 sometimes only works with certain scanners...

not sure why you think a particular sensor would affect voltages at the OBD2 port, AFAIK all the sensor wiring is outside of the OBD2 port itself.

what makes you think the engine is running rich?

Is the flashing CEL constant or intermittent? That could indicate a misfire(s).
Old 07-01-2019, 05:12 PM
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As an update I dropped it off at a mechanic to have them do an "inspection" shop didn't charge me because they weren't able to connect either.
Old 07-08-2019, 07:01 PM
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So the troubleshooting has continued,

I bought an oscilloscope and I am not seeing a square wave just a whole bunch of noise. This strongly suggests some sort of interference on Pin 2. I have orderd the OEM wire diagram book but have continued seeking answers. Front bank O2 sensors have been replaced the Gasoline smell is mostly gone Still need to get at the rear O2's the post cat Sensor is stuck in good. The bank 2 sensor 1 still needs to be unplugged, while I won't rule it out until it's changed I don't think that's my interferenece.

I have unplugged the SRS module with no change.

I am eyeing the ABS module connector with great suspicion. I found this dangling in the engine compartment, it was coated in corrosion. Most of that's cleaned up but I'm thinking it needs to be replaced.

Any thoughts?
Old 07-10-2019, 06:08 AM
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