1998 Honda Accord LX - 4 door - auto trans 4speed

This weekend my daughters car was having trouble shifting and the engine light came on. It shows P1739 and something else related to it that had to do with "gear ratio" problem. P1739 was the first code out of 2.This was a sudden thing and there were no problems before hand. I was able to drive it home, but found it was best to keep it in 2nd gear.

After looking on the internet, it seems that I could change the "3rd clutch pressure sensor". Can this possibly fix the problem?

Also found diagram and possible part #'s, but which one is it? I think its either #12 or #13. Which was is this transmission facing?

28600-P6H-003
SWITCH ASSY., OIL PRESSURE (TEXAS INSTRUMENTS)
28600-P7Z-003
SWITCH ASSY., OIL PRESSURE (TEXAS INSTRUMENTS)

Also when I checked the trans fluid, it seemed yellow brown. Should I change the transmission fluid? I heard if you wait too long, then it not a good idea.

 

P1739 is an electrical fault in the 3rd gear pressure switch circuit. This can be switch, connector, wiring, or PCM fault. Diagnostics are required to sort out which is the case.

Also if problem is intermittent, you may get a false signal from switch.

If you intend to DIY, suggest a shop manual to guide your testing. It runs for 2 pages of shop manual, but is electrically simple testing.

There should be 12V at the 3rd clutch pressure switch connector (switch connector disconnected) w/ keyswitch On. If 12V missing, problem w/ PCM or wiring.

Resistance of 3rd clutch pressure switch connector pin (released from harness) to ground should be 12 Mohm or higher (open switch). If switch shows a shorted condition, then replace switch.

good luck

good luck

 

Thanks for this info, I will take a look at it. As for the sensor, where is it? I see on the diagram there are 5 sensors, but I narrowed it down to #12 or 13... which one is it?

See attached diagram on first post

 

It is number 13 in the parts diagram. The 3rd clutch pressure switch is located at the bottom of the transmission.

 

I can't be sure from looking at manual. It is on front pax side of trans. It has single wire (blu/wht) on the harness side of connector.

If you plan any diagnostics, the shop manual is helpful. You can purchase a download manual in pdf form from automanualsource.com for $22.

good luck

 

Thank you guys!! ... Just to be sure, when I unplug the connector to that sensor, I should get 12 volts (ignition on, but engine is not running) coming from the wires?

If I get 12 volts, then I can take a chance and replace sensor?

 

You should also test the switch. It should show open circuit w/ engine off. If it shows a closed circuit in this condition, switch is definitely faulty. However, it may be that switch does not close (short) under pressure (trans in gear and operating) so faulty switch is still possible.

good luck

 

Ok I removed the connector and checked and got 12 volts from the wire. But when I measure resistance on the sensor, it is "open". Instructions says 10Mohn or greater is OK. Well I was hoping either for a short, or something like 50Mohm. What does "Open" mean?

 

Open is infinite resistance which is > 10 mohm so good.

It also means the switch is normal w/ Key On Engine OFF. However this test does not garuntee the switch functions when pressure is applied where it should switch to closed or shorted condition.

You would need to rig test wires to switch to allow a road test w/ VOM in the cabin w/ you. Test would look at voltage on the wire. It should stay 12V as long as switch is open, when switch closes voltage will drop to zero.

good luck

 

"Open" means open-circuit, for example the wires being disconnected completely.

For a real-life measurement, that just means the resistance is higher than the meter is capable of measuring. Without knowing the specifications of your meter, that might be 10 M-ohm or maybe 50 M-ohm. Meters that are capable of measuring very high resistance (50 M-ohm or 200 M-ohm) are more expensive.

(edit: Tex beat me to it)