|Trouble Code||Fault Location||Probable Cause|
|P0886||Transmission control module (TCM) power relay control circuit low||Wiring, short to earth, TCM power relay, TCM|
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What Does Code P0886 Mean?
Almost all of the latest makes and models with automatic transmissions use the PCM (Powertrain control module) and the TCM (Transmission control module) to control most of the shifting, pressures and other systems involved with an automatic transmission. The TCM is a computer which controls, monitors and adjusts various electrical components and systems specifically within the transmission system. The power relay control circuit is a circuit within the transmission electrical system. The electrical value(s) of the power relay control circuit must go beyond the functional parameters in order for the TCM to recognize a problem and then proceeds to turn on the check engine light in the instrument cluster with code P0886.
What are the common causes of code P0886 ?
- Defective TCM
- Defective TCM power relay
- Corroded or chafed wire(s)
- Corroded connection(s)
- Low system voltage
What are the symptoms of code P0886 ?
When this particular code is active you may or may not experience some of the following symptoms:
- Driveability issues
- Enters “limp” mode
- Will not upshift (Stuck in low gear)
- Low vehicle speed
- High RPMS
- Transmission slipping in and out of gear
How do you troubleshoot code P0886 ?
Whenever you are working with electrical components and systems, some of the basic tools you will need will are:
- OBD code reader
- Basic socket set
- Basic ratchet and wrench sets
- Basic screwdriver set
- Rag/shop towel
- Battery terminal cleaner
Whenever performing any repairs to your vehicle use must follow certain steps to keep you safe:
- Wear PPE (personal protective equipment)
- Chalk wheels to prevent rollaway vehicle
- Park vehicle on level and flat surface
BASIC STEP #1:
K.I.S.S, keep it simple stupid! Generally speaking, many problems with automatic transmissions resemble those of its counter-part, the manual transmission. That being said, you will want to start simple and check the automatic transmission fluid before doing anything else. Generally speaking, to check your fluid level, you will want to drive car enough to get vehicle up to normal operating temperature. Once vehicle is warmed up, park on a flat and level surface (to get accurate reading), place transmission in “PARK” or “NEUTRAL” (don’t forget the wheel chalks!) and let engine idle. Locate and remove dipstick (refer to service manual for location and specific procedures) and wipe it clean. Re-insert dipstick making sure it enters tube fully. Remove dipstick and insure fluid level is showing between checkered section between the “ADD” and “FULL” (refer to service manual for specific markings). If out of range, adjust fluid accordingly, by draining or adding fluid (refer to service manual for fluid specifications). Transmission fluid should be red and transparent. If fluid is extremely dark, milky or has a very strong burnt smell, it would be a good idea to drain fluid and replace with new. Clear codes using code reader and test drive. If code reappears, or everything checks out, proceed to next step.
BASIC STEP #2:
Check all fuse(s) and relay(s) associated with the TCM system. Typically, the fuse box will be under hood some where or under dash (refer to service manual for specific locations and specific procedures). Replace any blown fuses or relays which may show signs of overheating (burnt smell, melting). Clean any corrosion present. Clear codes using code reader and test drive. If code reappears or if fuse(s) and relay(s) are good, proceed to next step.
BASIC STEP #3:
Check your battery! Visually inspect terminals, wires and battery body for signs of damage or corrosion. If battery acid present, sprinkle baking soda and water on affected area, wipe with old rag and discard appropriately. Don’t forget rubber gloves! Battery acid will burn your skin!. Perform basic electrical test as follows: Connect your red positive multimeter end to (+) battery post and your black ground multimeter end to (-) battery post and measure voltage. With engine shut off you will want a voltage between 11.7v – 12.6v. With engine running, you will want a voltage between 13.5v -14.5v. If your values aren’t within these specifications, the problem may lie within your battery and/or charging systems and will need to be addressed. If they are, proceed to next step.
BASIC STEP #3:
Use your eyes! First, locate the components of the TCM system. Of course, these will vary between manufacturers but some of the common locations of TCMs are mounted to fender wells, firewalls or directly to the transmission housing. Common places for PCMs are in trunks, fender wells, firewalls, and under seats. Visually inspect the TCM and PCM for physical damage. Check wiring harness connections for signs of corrosion and/or loose connections. Make sure to disconnect your battery before repairing any wiring or circuit(s). Once repairs are complete, connect battery, clear codes using code reader and test drive. If code and/or symptoms reappear or everything checks out, proceed to next step.
BASIC STEP #4:
Check your circuit! At this point, it is more then likely that there is a high resistance present within the power relay control circuit. First , you will want to disconnect your battery. Next, identify wires used in the power relay control circuit. Once identified, unplug either end of the wire(s). Using your multimeter, measure resistance between either end of the wire(s). If multimeter shows 0L, this indicates infinite resistance. In other words, there is a open in the circuit which will need to be replaced/repaired. If resistance values are within manufacturer’s specifications, you more then likely have an internal short/open within the TCM or PCM themselves. If needed, repair circuit, clear codes and take for test drive. If code reappears, it would be a good idea to bring the vehicle to a reputable repair facility, as specialized equipment and procedures will be needed to further diagnosis.
Codes Related to P0886
- P0882 – Transmission Control Module (TCM) Power Input Signal Low
- P0883 – Transmission Control Module (TCM) Power Input Signal High
- P0884 – Transmission Control Module (TCM) Power Input Signal Intermittent
- P0885 – Transmission Control Module (TCM) Power Relay Control Circuit / Open
- P0887 – Transmission Control Module (TCM) Power Relay Control Circuit High
- P0888 – Transmission Control Module (TCM) Power Relay Sensore Circuit
- P0889 – Transmission Control Module (TCM) Power Relay Sensore Circuit Range / Performance
- P0890 – Transmission Control Module (TCM) Power Relay Sensore Circuit Low