Powertrain, generic · Transmission

P0737 TCM Engine Speed Output Circuit

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. P0737 is the general circuit fault of this output; low and high are P0738/P0739. Not to be confused with the engine speed input at the transmission module (P0725 ff). A tachometer or dependent display then reads wrong or nothing, while driving is usually unaffected.

Likely causes

Wire to the receiver open or shorted
Receiver (e.g. instrument cluster) shorted internally
Connector corroded
Driver stage in the transmission module faulty

Symptoms

  • Tachometer or dependent display not working or wrong
  • 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

P0738P0739P0654P0725

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