98 Legacy GT half cluster failure

98 Legacy GT. 5psd. 172K. Mrs. flexi reported that the check engine light recently turned on. She pulled the OBDII codes and found plugs 3 & 4 misfire, (P0303 & P0304) and vehicle speed sensor 1 & 2 (P0500 & P1540) failure. She also reports the speedometer stopped working at the same time as the check engine came on. I did a quick check and confirmed the speedometer was not working.

The misfire codes I know about. The coil terminals look corroded. I polished them up again and squirted in some dielectric grease. Coil & wires were last replaced at 137K, platinum plugs at 120K.

How long do subie wires last? How about platinum plugs?

I don't understand two speed sensors dying. What is the likelihood of that happening?

SS1 is on the backside of the transfer case, and SS2 is on the top of the transaxle. SS2 runs the speedometer. I would guess that SS1 eventually goes to the ECU. I think (crappy Haynes) that one or more of these sensors are buffered before going to the ECU. I don't have the ECU pinout.

Could a mis-seated cluster connector cause the speed sensor codes? I think there is only one fuse to the cluster, and the tach does work.

Any suggestions? Places to look? Common failure point? I really want to get this fixed... Or pull the plug...

Thanks!

I always had issues with my old subaru (94) going through plug wires at an inordinate rate.

How's the charging system?

I once discovered that the alternator on my 97 Legacy was toast when some of the warning lights came on and the speedo and tach dropped to 0.

There was enough voltage to run the car, but not the dash. Shortly thereafter it started running rough and then stalled.

flexi wrote: How about platinum plugs?

If they're single platinum plugs, #3 and #4 probably eroded away from the waste spark ignition.

1) Clean up a few of the old engine compartment grounds.

2) The only time I've had misfire codes on my Subies is when the valves went bad. The '97 2.5L had adjustable valves (shims which suck). When was the last time the clearance was checked? This is for the misfire codes.

Hocrest wrote: How's the charging system? I once discovered that the alternator on my 97 Legacy was toast when some of the warning lights came on and the speedo and tach dropped to 0. There was enough voltage to run the car, but not the dash. Shortly thereafter it started running rough and then stalled.

I don't know yet. How do you check it? Lights brighten at increased engine speed? Or is that for the voltage regulator?

fornetti14 wrote: 1) Clean up a few of the old engine compartment grounds. 2) The only time I've had misfire codes on my Subies is when the valves went bad. The '97 2.5L had adjustable valves (shims which suck). When was the last time the clearance was checked? This is for the misfire codes.

On 1) know where they all are? On 2) beats me. I couldn't find evidence in my records of the valves being adjusted. I'll check on that.

Anyone have an idea why both speed sensors crapped out?