Engine Controls - DTC P0170 Ground Improvement

SOURCE: Kia Technician Times

TITLE: DTC P0170 Ground Improvement

APPLIES TO: 95-97 Sephia

SERVICE TIP:

CONDITION

Some 1995 - 1997 vehicles have experienced repeat occurrences of "Check Engine" light illumination where a DTC P0170 - Fuel Trim Malfunction was retrieved.

CAUSE

This condition is caused by high resistance in the MAF sensor ground circuit which results in excessive negative fuel trims.

CORRECTIVE ACTION

NOTICE
- A high negative fuel trim is typical of a poor ground connection.
- Before starting ground improvements, remove any previous ground additions from the EGI wiring harness.

1. After retrieving a P0170 code, make note of the freeze frame data.
a) Record the short fuel trim (SFT) and long term fuel trim (LFT) percentages.
2. Start the engine and allow it to fully warm-up and switch to closed-loop operation as indicated on the scan tool.






3. Using a digital voltmeter, measure the voltage drop from G103 to the MAF sensor connector C135 Pin No. 5.
a) Connect the positive lead to connector C135 Pin No. 5 and the negative lead to G103.
b) If the reading is above 0.060 volts, the EGI harness grounds will need to be improved.
c) If the reading is less than 0.060 volts, then the DTC P0170 has been caused by some other malfunction.






4. Turn the engine OFF. Remove the ground lug at G103 from the bracket.
5. Remove the bracket from the head, clean the bracket mounting surfaces then re-attach the bracket to the head.
6. Using a pencil torch or high wattage soldering gun, solder the four wires to the ground lug and re-attach the lug to the bracket.











7. Remove the pin lock and extract Pin No. 5 from connector C135.
8. Solder the pin to the wire at the crimp.
CAUTION: Do Not solder the pin opening closed.
9. Re-install Pin No. 5 and pin lock into connector C135 and re-install the connector onto the MAF sensor.
10. Locate junction connectors C252 and C257 (taped up to the harness to the right of the PCM).
NOTICE: Both connectors have BLK/YEL wires.






11. Remove the tape from the connectors.
12. Remove the jumper connector from one of the connectors.






13. Remove the pins from the connector and discard the plastic housing. Install the pins directly onto the jumper connector.






14. Solder wires to crimp-on connector pins and to the jumper connector.
15. Tape-up the connection with electrical tape and tape back into the harness.
16. Repeat steps 12 through 15 for the other connector.






17. On 1996 and 1997 vehicles, locate splices S100, S105 and S106 in EGI wire harness.

NOTICE
Only 1995 Vehicles have splice S106 (BLK/YEL) wires.

18. Carefully cut through the harness insulation at the approximate area shown and separate the splices.
19. Solder each splice separately then apply electrical tape over each splice.
20. Start the engine and allow it to fully warm-up and go into closed-loop operation as indicated on the scan tool.
21. Monitor the short fuel trim (SFT) and long fuel trim (LFT) using the scan tool.
22. The combined fuel trims should not be more negative than (-7%).
23. Allow the engine to idle long enough for the engine cooling fan to cycle ON and OFF three to four times.






24. Using a digital voltmeter or scan tool, measure the voltage drop from G103 to the MAF sensor connector C135 Pin No. 5.
a) Connect the positive lead to connector C135 Pin No. 5 and the negative lead to G103.
b) The reading should be less than 0.060 volts. If okay, clear the DTC P0170.
c) If the reading still exceeds 0.060 volts, replace the EGI harness.

NOTICE
- The topics covered here are designed to assist you with the diagnosis and repair of common vehicle conditions. Just because a condition is described here, do not assume that it applies to your vehicle, or that your vehicle will have that condition.
- In all cases, the procedures in the applicable system should be performed first.

CAUTION
VEHICLE SERVICING PERFORMED BY UNTRAINED PERSONS COULD RESULT IN DAMAGE TO THE VEHICLE.