DTC code P0740 has now appeared. Looking through the manual (14-74) I see it appears to be tied to the A/T Lock-Up control system. D4 indicating light appears OK. Without having the pressure testing equip is there anything else I can check. Would pulling out the Lock-up Control Solenoid Valve Assembly and having a look-see accomplish anything? This looks like it may be serious! I notice the car shifts in/out of final gear (lock-up) often and sometimes I think too late. Any help with matter would be greatly appreciated.

Tom

 

For your 99 Civic, the relevant troubleshooting page is actually 14-99.

Did you already check whether the dash D4 light blinks an additional transmission code when the service connector is jumped?

Have you cleared the ECU to ensure that the CEL code repeats?

You might want to take the car to a reputable transmission shop to have them check the transmission hydraulic system. But first, replace the transmission fluid with a Honda-compatible ATF, clean the lock-up solenoid valve and its gasket/filter, then test the solenoid (see diagrams). The solenoid cost about $150 at Majestic Honda.

Also note that the Civic AT was not very good right out of the box, so some of the late shifting may actually be "normal". Finally, if you were to find that replacing the transmission is necessary, you can probably purchase a replacement at a low price because most people replace their Civic AT with a MT.

 

Ron - Thanks first of all. Yes 99 is correct but they test the same. Not real sure what the service connector is or where it goes (under dash passenger side?). Can I just jump the two circuits with wire? The D4 dash light does come on for a couple of seconds when the ign is on then goes off and i t does not blink. Yes, I have cleared the PCM/ECU and the DTC repeats when driven about 6-10 miles. I was going to drain/replace the A/T oil that's why I inquired about the oil on a previous post. I will (not right away) check the solenoids and clean filter on the lock-up control ***'y and reply back.

 

The 2P service connector is used to retrieve both CEL and D4 codes and to check/adjust the ignition timing. You can use a short piece of wire or a paper clip to jump the two terminals of the connector (see CEL link in my signature), which is located above the ECU behind the front passenger kick panel.