BlackMacks

iTrader: (3)

So I finally put the wraps on my 98 Quest VQ35DE into my 02 Max, and aside from some lights: SES/TCS off/SLIP that I'm pretty sure I know how to fix ( THANKS SEARCH FEATURE ) I do have one that's kinda got me stumped right now- no tach reading.

Not knowing anymore about these cars than I do yet, and not finding anything relating to this on searches, I'll just throw this out here: I've already double- checked my harness plugs into those two sensors that mount into the sides of the heads roughly where the cams would be, and I can't imagine the car running as well as it does without a good crank position sensor, so I don't think that's the problem either.....

What'd I miss? Where's my tach signal generated from? Cluster problem? Anyone?

Thanks,

BlackMacks

iTrader: (3)

bueller?

pepox369

anyone knows this??

good luck!

BlackMacks

iTrader: (3)

Pep- thanks for the bump.

I went ahead and printed the DTC list and this evening if I have time I'm gonna plug in the scanner and see if the answer lies in my SES light, above and beyond the "left my gas cap off" explanation the previous owner gave me.

I traced the tachometer signal from the multi-display to its ecu pin-out, but then I lost it in the engine wiring harness schematics. The circuit appears to hit both the CPS and one of those cam position sensors, but I find it strange that the car runs well if one (or both) of those sensors is faulty. Altho, come to think of it, I *might* have an explanation for that.

Guess we'll see.

NmexMAX

iTrader: (22)

Interesting ... 98 VQ35 into an 02 Max.

BlackMacks

iTrader: (3)

Yeah, it wasn't exactly a straight-up swap, lol, compounded by the fact that I'd only lifted the hood on the car once before that.

Care to hear the specifics?

AEMAXIMA01

iTrader: (3)

The VQ35 didn't exist in 98. please explain...

BlackMacks

iTrader: (3)

Hmm, sorry for any confusion, the "info" I have access to does call the 08 Quest 6 cyl. a VQ35DE, but I'm not strong enough in my knowledge base to say definitively.

NmexMAX

iTrader: (22)

08 or 98?

mattbaga

no tach reading could be caused by a faulty transmission speed sensor...i know in mine both front wheel speed sensors were broken for a year so my speedo wouldn't work, (which i got about 30k free miles from), but i was able to judge my speed from my tach (speed sensor in trans)

BlackMacks

iTrader: (3)

Aw crap, I just realized what I typed...... _08_ Quest, my bad, not 98, jeez.... sorry y'all

Matt- thanks for the reply- my speedo works perfectly, but the tach's dead. I plugged the scanner in last night and got P0335, which wasn't unexpected, given the CPS problems I had between the two engines and the install, but strangely enough, the scanner was able to display my engine RPM no problem, car idled at 700-ish and I was able to record all the way up to 4k or so when revving in park.

How would the OBD-II port receive the tach signal but the tach wouldn't? More scrutiny of the wiring schematic is in store....

NmexMAX

iTrader: (22)

Looks like your cluster wiring may be faulty.


But you knew that...

BlackMacks

iTrader: (3)

Y'know, I was thinking that same thing, at first, but I got to thinking (dangerous pastime, I know) about what I saw in the wiring diagrams, and this little jewel of info: I also pulled a C1130 error code, which says "CAN Communication line or ECM"

I talked to a co-worker of mine about the scanner displaying rpm while the tach would not, and while not missing a beat, he said "cam position sensor", the obd2 port gets its rpm signal straight from one of the cam position sensors, while it takes communication between one and the crank position sensor to make the tach work. Since my crank position sensor appears to have issues communicating with the cam position sensor, I get the codes mentioned, along with no tach, and yet the car still runs and drives.

At least, it sounds good when I say it like that....

CAN (Controller Area Network) is a serial communication line for real time application. It is an onvehicle
multiplex communication line with high data communication speed and excellent error detection
ability. Many electronic control units, such as Engine Control Module (ECM), Transmission Control
Module (TCM) and, if equipped, Anti-Lock Brake Systern/Traction Control System (ABSITCS) Unit
and I35 with Vehicle Dynamic ControlIAnti-Lock Brake SystedTraction Control System
(VDCIABSITCS) Unit, are equipped onto a vehicle, and each control unit shares information and links
with other control units during operation (not independent). In CAN communication, control units are
connected with 2 communication lines (CAN "H" line, CAN "L" line) allowing a high rate of
information transmission with less wiring. Each control unit transmitslreceives data but selectively reads
required data only.

Sorry for the bad paste, stupid Mitchell program. So, I've gone ahead and placed an order for my 08 Quest CPS after verifying it will plug into my existing harness. It's a low-profile version of my CPS, which will come in handy due to its new mounting location.