Here's the scoop on the P0340 you need to check it this way:
The Electronic Ignition (EI) module supplies a signal to the PCM whenever it determines that
cylinder No. 4 fired on its compression stroke. Because of opposite coil tower polarity, the
simultaneous firing of cylinders No. 1 and 4 are of opposite polarity as well. Under the most
conditions, the waste spark cylinder fires before the compression cylinder in sequence. The EI
module can determine this polarity sequence and voltage amplitude by using capacitive pickup plates
located under cylinders No. 1 and No. 4 coil. If module senses a positive and negative sequence and
high negative spike when cylinder No. 4 is on TDC, it pulls the PCM cam signal to ground signaling
that cylinder No. 4 has just fired on compression. This signal along with the double pulse received
from the CKP sensor, synchronizes spark and fuel timing.
DTC will set if the PCM voltage on cylinder No. 4 signal wire is not pulled to ground (cam signal
pulse) when engine has been cranking for 5-10 seconds or when engine is running. Cam signal is
continuously checked when crankshaft sensor pulses are received by the PCM, except under
1. Connect scan tool. Start and operate engine for one minute. Using scan tool, check if DTC is
active. If DTC is active, go to next step. If DTC is not active, problem is intermittent. See
2. If engine misfire is present, check for a fault condition on cylinder No. 1 or No. 4. Check
wires, plugs and cylinder compression. If engine misfire is not present, go to next step.
3. Install a jumper wire between IC module terminal "D" and harness connector. With engine
running, observe 7X counter by using test light. Connect test light to ground and momentarily
touch jumper wire. Observe 7X counter on scan tool. If 7X counter resets to zero when touched
by test light, check tightness of harness connector terminal to EI module or faulty EI module. If
7X counter does not reset to zero, go to next step.
4. Check cylinder No. 4 signal circuit between PCM and IC module terminal "D" for open, short
to ground or short to voltage. Repair as necessary. If circuit is okay, check tightness of harness
connector terminals to PCM.
When attempting to diagnose an intermittent problem, use scan tool to review malfunction history
information. This data can be used to duplicate a problem.
Tuesday, March 15th, 2011 AT 7:15 PM