Powertrain, generic · Transmission

P0739 TCM Engine Speed Output Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Some transmission modules pass an engine speed signal on to other devices such as a tachometer over a wire of their own. CARB requires output circuits to be checked. No manufacturer document available to us uses P0737–P0739 – engine speed is shared over CAN today; the description follows CARB and the engine module's own speed output (P0654), which sends, for example, two pulses per revolution. P0739 means this output is too high, typically shorted to positive or, depending on the driver, open, so it can no longer switch to ground. The opposite is P0738, the general fault P0737. A tachometer or dependent display then reads nothing or full scale, while driving is usually unaffected.

Likely causes

Output wire shorted to positive or open
Receiver faulty
Connector corroded
Driver stage in the transmission module faulty

Symptoms

  • Tachometer shows nothing or full scale
  • Warning lamp depending on manufacturer
  • Usually no effect on driving

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–300
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

engine speed output circuittachometertransmission control module

Related codes

P0737P0738P0654P0725

References: law.cornell.edu, saabwisonline.com.