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RLM67 09-24-2013 01:04 PM

Replacing input/output speed sensors
Hello again,

Got a query that I think I may have solved myself, but am soliciting some additional feedback from WJ drivers out there. Wife was driving our '00 GC 4.7 home when it started 'bucking' at freeway speeds, 'Check engine Light' appears. I retrieve the codes--p0320 [no crank reference signal @ PCM], and p0700 [check transmission DTCs]. After some research, I've found that this is a common/related failure and can usually be remedied by replacing both sensors. The Chilton manual I reference so often states that if a DRBIII scanner doesn't retrieve any fault codes, the problem could simply be the TCM. These are inexpensive and relatively easy fixes, but I just want to make sure I'm running in the right direction. BTW, I took it out last night and drove it for a good 15 miles and had no problems. Any thoughts?

Frango100 09-24-2013 02:56 PM

Re: Replacing input/output speed sensors
You need to have it scanned to know which fault the TCM has stored, otherwise its just shooting in the dark and most probably spending more money on parts then necessary
The crank sensor is a sensor on the engine, while the input/output speed sensors are on the transmission.
I would check the connector on the crank sensor, but maybe even better to replace it right away, because it will let you stranded at some point. Its mounted above the starter and the starter needs to be removed to get access to the sensor.
Best is to get OEM sensor.

RLM67 09-24-2013 06:45 PM

Re: Replacing input/output speed sensors

Thanks for the input--it turned out to be the sensors; replaced each of them, MIL disappeared, codes cleared. Will definitely look into checking/replacing the camshaft sensor--looks like a relatively easy fix as well.

Thanks again,

Richard M.

Frango100 09-24-2013 07:21 PM

Re: Replacing input/output speed sensors
You meant crank sensor?
You where lucky that the speed sensors solved the problem, could have been the TPS as well

RLM67 09-25-2013 03:13 PM

Re: Replacing input/output speed sensors

Thanks for your advice. Replaced the I/O sensors, engine light went out, codes cleared. Wife was driving the GC to work this morning and called to tell me the MIL was back on and that the initial symptoms had returned.. Retrieved the same codes. All info I'm finding does point to the crankshaft sensor. So. I'm going to replace that tomorrow. Thanks for the heads up.


Frango100 09-25-2013 06:51 PM

Re: Replacing input/output speed sensors
Did you clear the fault codes after replacing the sensors? Eventough the check engine light went out, it will still keep the fault codes in its memory. Some faults do disappear after many key cycles and no fault, but best is to errase the memory after changing a part, so that you start with a clean sheet.
Crankshaft position sensor signal also goes to the TCM, so could explain the P0700 fault code.
You can easily remove the starter by only removing the two bolts which keep it in place. No need to remove the wires or connector, however first remove the negative battery terminal to prevent a short.
When starter is removed, you will see the crank sensor. Best is to use OEM sensor.

RLM67 09-26-2013 02:18 PM

Re: Replacing input/output speed sensors

Replaced the crankshaft sensor--dropped the starter down and accessed the sensor [it was a little tricky getting it out]. Installed the new one--no MIL and the p320 & p700 fault codes have cleared after one trip. You've been a huge help--much thanks.


Richard M.

Frango100 09-26-2013 09:41 PM

Re: Replacing input/output speed sensors
Good to hear its fixed:thumbsup:.

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