My dad has a 1997 F150 XLT 4x4 with a 4.6 and a 4R70. This morning, he brought it home from the store and said it wasn't running right. The check engine light was on(P0500, Vehicle speed sensor "A" malfunction), the overdrive off light would flash on and off after you drove it a few feet, and it wouldn't go into 4WD. It shifts hard, whines a LOT when it's moving, and had a few other small issues like that. At the exact same time, the ignition cylinder(I think) started having problems. It acts like the key is in the slot, dinging when you open the door, etc. Also, when I hit the lock button, the doors lock, but the security system doesn't engage, so I'm pretty sure it thinks the key is in there still. Also, the radio stays on when the door is open and the key is out. We've been having issues with the ignition for a few months, like, we can pull the key out with it running, etc. But this is the first time it's acted like this, and since the two problems started happenning at the exact same time, my dad(his truck) thinks they're related. Any ideas guys? I've got a post going in transmissions too, but I figured since there were electrical issues, I'd post it here too.

 

They're not related. Ford had lots of problems with lock cylinders from '92-99, but aftermarket replacements aren't too expensive. If he wants to keep the same ig.key, he'll either need to pay a locksmith or get a new ig.lock cyl. from Ford. I just put one in my '99 CV, but he can pay the dealer to assemble & install his. I'd guess they'd charge 1/2 - 1 hour to do it, on top of the price of the part.



Crawl under the truck & inspect the wiring going to each of the sensors on the trans. #101 (OSS) in the 1st diagram & the black VSS at the far L center of the photo.

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Alright, checking that now. I'm gonna just replace the lock cylinder and ignition switch with an aftermarket one, if that solves the problem, I'll have the stealership sell me one that matches the door locks or whatever. Thanks!

 

Wiring on both of those sensors was fine, along with all other sensors I could get to. Any other ideas?

 

Diagnostic Trouble Code (DTC) P0500/P0501 indicates that a VSS malfunction has been detected.

NOTE: Delayed engagement or no vehicle movement can be caused by a transmission concern. Harsh shifts and/or erratic speedometer can be caused by a failed speedometer or an open or intermittent ground within the instrument cluster on vehicles with electronic readout.

Possible causes:
-- Open in VSS+/VSS- harness circuit.
-- Short to GND or SIG RTN in VSS+/VSS- harness circuit.
-- Short to PWR in VSS+/VSS- harness circuit.
-- Damaged VSS.
-- Damaged PCM.

DIAGNOSIS:
1. Key off.
2. Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires. Service as necessary.
3. Install breakout box, PCM disconnected.
4. Disconnect VSS.
5. Measure resistance between Test Pin 58 (VSS+) at the breakout box and VSS+ circuit at the VSS vehicle harness connector.
6. Measure resistance between Test Pin 33 (VSS-) at the breakout box and VSS- circuit at the VSS vehicle harness connector.

> Each resistance should be less than 5.0 ohms. If not, service open circuits, clear DTCs, & test drive.

Obviously, you don't have a breakout box, but all you have to do is disconnect the PCM connector & probe the correct terminals. Pin 33 is VSS- Pk/Or, and pin 58 is VSS+ Gy/Bk. The PCM connector is the tall skinny one behind the battery that goes thru the firewall with a 10mm or 11mm bolt head in the middle. Just back the bolt out to separate the connector & access the pins. Don't turn the key on while anything is disconnected.

If resistance is below 5 Ohms on both circuits...
CHECK HARNESS CIRCUITS FOR SHORTS TO GROUND, SIG RTN AND POWER
1. Key off.
2. VSS disconnected.
3. Breakout box installed, PCM disconnected.
4. For vehicles with purge flow (PF) sensor, disconnect the PF sensor (refer to the schematics in Pinpoint Test HW to view PF sensor connector shape).
5. Measure resistance between Test Pin 58 (VSS+) and Test Pins 24, 51, 76 and 103 (PWR GND).
6. Measure resistance between Test Pin 58 (VSS+) and Test Pin 33 (VSS-).
7. Measure resistance between Test Pin 58 (VSS+) and Test Pin 91 (SIG RTN).
8. Measure resistance between Test Pin 58 (VSS+) and Test Pin 71 (VPWR).
9. Measure resistance between Test Pins 33 (VSS-) and 71 (VPWR) at the breakout box.

> Each resistance should be greater than 500 ohms. If not, service short circuits, clear DTCs, & test drive.

VPWR is pin 71 R, Power Ground is pin 24 Bk/Wh, SIGRTN is pin 91 Gy/R. You don't have a PF.

CHECK VSS RESISTANCE
1. Key off.
2. VSS disconnected.
3. Measure the resistance of the VSS.

> Resistance should be between 170 and 270 ohms. If not, replace the VSS. If it is, reconnect everything, clear DTCs, & test drive.

That's where the official service procedure ends, but if it still throws the code, I'd pull the VSS & inspect the gears.

If you want a Ford service CD that contains all that & MUCH more, you can try to dl it free, but this BBS doesn't allow me to post the link to that site. Or you can e-mail me by clicking my username, to the far L.

 

Okay... After replacing the ABS Wheel speed sensor in the differential housing, the speedometer works, but all the other problems remain. I removed the transfer case actuator from the transfer case, and manually put the truck back into 2H to get it drivable, but beyond that, I haven't accomplished anything.

 

Alright. The key in issue I solved by kicking the GEM and fusebox. I figured this meant that something was wrong with the GEM, and that might be affecting my 4x4 system as well, so I replaced the GEM. Now the problem with the ignition switch is still gone, but the 4x4 issue is still there. I've replaced the GEM, VSS, ABS Wheel speed sensor in the rear, and the transfer case actuator thingeh. My problem is still there, exactly like it was when I started. Now, I noticed last night(the 4x4 and Low Range lights are on) that when I wiggle the fusebox/GEM, the 4x4 light will flicker on and off. Now I'm thinking I may have an issue with the wiring going to the GEM. Does that sound plausible? How would I diagnose/repair that? Also, when I have the cruise control engaged, putting the vehicle into neutral will not disengage it. Could this be a sign of a bad Neutral Safety Switch / Back-Up Light Switch? If the computer didn't know it was in neutral, it wouldn't allow me to switch out of low range, would it? I'm hesitant to keep throwing parts at it, but I'm also running out of options here. Any ideas where to go from here? Oh, it hasn't thrown any codes since the P0500 that I cleared after replacing the speed sensor.