P0739
UniversalThe Powertrain Control Module (PCM) or Transmission Control Module (TCM) has detected an absence of pulses from the Timing Reference High Resolution Signal B circuit.
Medium SeverityThis code indicates that the engine's computer, or specifically the Transmission Control Module, is not receiving the necessary high-resolution timing pulses from a particular sensor, likely within the transmission. This lack of signal prevents the transmission from accurately determining its speed or position, leading to erratic shifting or a lack of power.
⚠️ Before You Begin (Safety First)
Always exercise caution when working on a vehicle. Ensure the vehicle is on a level surface and properly supported with jack stands. Disconnect the battery before performing any electrical work. Allow components to cool before touching them. Consult a professional if you are unsure about any repair step.
Common Symptoms
- Check Engine Light illuminated
- Harsh or erratic shifting
- Transmission slipping
- Vehicle stuck in 'limp mode'
- Delayed engagement of gears
- Loss of power
Common Causes
- Faulty transmission speed sensor (Timing Reference High Resolution Signal B sensor)
- Damaged or corroded wiring/connectors to the sensor
- Internal transmission mechanical failure preventing sensor signal generation
- Faulty Transmission Control Module (TCM)
- Low or contaminated transmission fluid
Frequently reported on: General/Universal
Diagnostic Steps
- Check transmission fluid level and condition.
- Visually inspect all wiring and connectors leading to the transmission, especially any visible speed sensors, for damage, corrosion, or looseness.
- Clear the code and test drive the vehicle to see if the code returns.
- If accessible, disconnect and inspect the relevant speed sensor connector for bent pins or corrosion.
- Consult a service manual for the location of 'Timing Reference High Resolution Signal B' sensor and its testing procedures (e.g., resistance check, signal output).
👨🔧 When to Call a Professional
If after checking basic wiring and connectors the code persists, or if transmission fluid levels are abnormal, seek professional diagnosis immediately as internal transmission issues may be present.
Commonly Asked Questions
What is a 'Timing Reference High Resolution Signal B'?
It's a precise electrical signal sent by a sensor, often within the transmission, that the vehicle's computer uses to accurately monitor rotational speed or position for proper shifting and operation.
Can I drive with P0739?
It is not recommended to drive with this code for extended periods, as it indicates a significant transmission issue that could worsen or cause further damage.
Is it always a faulty sensor?
While a faulty sensor is a common cause, the problem could also stem from damaged wiring, a connector issue, or less commonly, an internal transmission mechanical problem preventing the sensor from detecting movement.
What's the first thing I should check?
Begin by checking your transmission fluid level and condition. Then, visually inspect the wiring and connectors around your transmission for any obvious damage.
How expensive is this repair?
The cost can vary greatly. Replacing a transmission speed sensor might be a few hundred dollars, including labor, but if it indicates an internal transmission failure, costs could be significantly higher.