Many vehicles have a control module for the automatic transmission
called a transmission control module (TCM). The engine control module
(ECM) communicates with the TCM to monitor the automatic transmission
for faults. If the TCM detects a fault in the automatic transmission and
sets a transmission related fault code, the ECM is informed of this
also and sets a P0700 in the ECM memory.
This illuminates the Malfunction Indicator Lamp (MIL) to let the
driver know there is a problem. If this code is present and the MIL
(Malfunction Indicator Lamp) is illuminated that basically means there
is at least one transmission code set in the TCM's memory. P0700 is an
informational code only. It doesn't point to a direct fault in the
engine, only a general fault in the transmission. More diagnosis is
necessary to identify what the transmission fault is. This requires a
scan tool that will communicate with the transmission module.
Symptoms of a P0700 DTC may include:
- Malfunction Indicator Lamp (MIL) illumination
- The transmission may exhibit drivability problems like slipping, etc.
More often then not, the cause of this code is that there is a
transmission problem of some kind. The TCM detected the problem and set a
code. P0700 means that a fault code is stored in the TCM. However this
doesn't rule out the possibility of a failed PCM or TCM (unlikely).
For a P0700 the only real solution is to acquire a scan tool that
will communicate with the transmission control module. Extracting this
code from the TCM will be the first step in repairing the fault in the
If the TCM compatible scan tool will not communicate with the
Transmission Control Module then that is a good indication that there
may be a fault with the TCM itself.