cbarner3

So I'm 90% sure my PCM is going bad. It is throwing the infamous p1698 code and showing all the signs with random stalling, and gauge cluster acting crazy. Can I pull a PCM out of another Jeep Cherokee and plug it in mine to test and make sure its the PCM without having it flashed? My cherokee is a 98. What year PCM's would I be able to use?

Gee oh Dee

Try and get another 98, but for you 97-99 *should* work iirc.

DFlintstone

Hey...you see all sorts of stuff here....I saw that mentioned as a CPS issue somewhere. IIRC he could unplug the his CPS and his gauges world start working. Idk...easy enough to try though.

P1698 No CCD Messages Received From PCM Bus communication failure to PCM. A "Companion DTC" was set in both the ECM and PCM.

Being that I'm pretty much clueless on the thing, I might try disconnecting the battery overnight and see if that does anything...

cbarner3

Well it all first started when i was driving and i got a check engine light and check gauges light. I noticed the battery voltage was at 9, so i checked the battery and it was good and ended up replacing the alternator. The check engine light stayed on so i got it scanned and it showed 2 codes, 1 for the cps and the other for the tps so i replaced both. Started stalling randomly and now I scanned it again and am getting a p1698, high voltage, and ecm codes. Ive noticed that randomly, one of the gauges ie speedo, battery, and gas will stop working momentarily and then start working again. So now I am lead to believe it is the PCM failing. What would happen if I found a 98 jeep like mine and used the PCM without reflashing or anything? Im talking as far as long term use not just temporarily. I am thinking about going to a junkyard and pulling one as I hear the autozone ones are junk.

Turbo X_J

Did both parts actually test bad? A fault code is set because of a problem in a circuit, not always a component. If say the problem is actually in one of the connectors leading to the PCM, you will be replacing a lot of parts and never fix the problem.

cbarner3

The guy at the parts store said they both showed fault codes but I didn't see the scanner.

On another note, was driving to go pick up the new PCM when i heard a slapping noise so i pulled over and turned the jeep off and noticed the serpentine belt was sliced in half. While looking at it, the coolant hose on the thermostat housing blew off and spit brown muddy coolant everywhere. I got it back to my driveway where it died and now I cannot get it to re start even after cooling down. It turns over just wont crank. Any ideas?

DFlintstone

Holy cow! Well, put a new belt on it, replace the hose and check the others for soft spots....refill with fresh 50/50 coolant mix. If you pull the lower hose off the rad and get after it with a garden hose you can flush it better. The drain might not work so well. Maybe the distributor and/or coil got wet? Sometimes I bring the dizy cap in and clean it just like a dirty dish. Sorry, I hope someone else here can help....

Oh, and...I hear getting the tps wet can be bad...Idk, a quick splash should be OK, I just saw it mentioned in regards to the car wash.

cbarner3

Well the motor turns over but when i turn the key to accessory, none of the gauges on the dash work. Like I have no battery, oil pressure or anything. any ideas? Think the PCM fried?

Radi

Disconnect the CPS and see if your gauges come back. If they do, get a new CPS from *the dealership*, not aftermarket.

What I suspect happened- and this is a longshot guess- is the bad alternator created a low voltage condition, leading a handful of sensors to set codes, which you replaced with aftermarket sensors, creating another layer of problems. In particular the aftermarket CPS' are spotty at best.

DFlintstone

X2^ I did see one post at least where a guy was sure unplugging the CPS brought his gauge function back. IIRC, his were goofy though, not DOA.

I assume you mean "key to ON", not accessory. Does other stuff work? I'd make darn sure I checked the fuses well, including the mini fuses under the hood in the PDC. I've never seen a 99, but aren't there connections there at the fuse-box/PDC that get funky?

I found another>>>P1698......No CCD Messages Received From PCM<<<<<

cbarner3

well if it were a fuse, wouldn't it not work all the time? The gauges not working seems to be spotty. My check engine light is on and its thowing that p1698 code so im assuming that the PCM is bad but it also is saying the ECU is bad.