CODE HELP!!!

Code 29 - Vehicle Speed Sensor (VSS) is an electronic sender mounted on the speedo pickup gear on the trans. It works the cruse control for both 5 speed and auto trans cars. The VSS is used to tell the computer to speed up the idle as you slow to a stop. This helps keep the engine from stalling when you slow down for a stop sign or stop light.
Check to see if the electrical connector is plugged into it. Clean the connector & contacts with non flammable brake parts cleaner prior to replacing the sensor, as that may fix the problem. The sensor cost is under $30 and it is easy to replace.

Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.

The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel. Many times the end result is an engine that runs pig rich and stinks of unburned fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.

Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

Code 95 - the 95 code is because at one time or another the fuel pump relay hiccupped and didn't provide power the pump when the computer told it to run. Sometimes this is a one time thing, other times it is a no run or runs poorly condition.

To help troubleshoot the 95 code, follow this link for a wiring diagram http://www.autozone.com/images/cds/gif/large/0900823d80195960.gif

JAZ 5.0 said:

Ok, well the code 29 - VSS I think is because the tranny is leaking from the VSS. So I'm not worried about that.

Code 41 and 91: I'll change the O2's and see if that does it. I failed to mention my cats are toast; will that effect the O2's?

and Code 95: Should I worry about it? It idles ruff sometimes and other times it doesn't, but I know that can be so many things. Should I replace the fuel pump? It's stock with 146,xxx miles...

Thanks for the help

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Unless there is oil inside the electrical connector for the VSS, an oil leak won't hurt it. The O ring that seals the VSS to the transmission is probably the source of the leak. Oil inside the electrical connector can be a problem. Clean the wiring connections, clear the codes & re-test. If it fails again, replace the VSS sensor.

The O2 sensors will hurt mileage & often have an effect on the idle quality.

Changing the fuel pump will not fix the 95 code. If you re-read the code notes, it said that the pump lost electrical power at one time or another. That could be a bad fuel pump relay, fuse link or electrical connection. Or it could be a phantom freak occurance that just popped up. Clear the codes and drive it for a few weeks & re-check them. If it comes back, then start to look at the relay & wiring.

JAZ 5.0 said:

Hey thanks for the help. I'll just clean up the VSS and replace the O2's. I just wasn't sure about the code 95 so that's why I was asking. I'll just clear the code and check later if it pops up again. But is code 95 Fuel Pump Secondary? because that's what the scanner referred to; does that just mean what you told me, the relay or wiring?

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Either one can trip the code. A broken wire or bad connection can do the same fault as a bad relay. The computer sees no power being sent to the fuel pump while the engine is running.