4 weeks ago after all 6 Electronic Ignition Coils had been replaced, it was suggested that I get a transmission flush as the car seemed to be a bit “sluggish”.

As the transmission had been flushed earlier in the year, I didn’t worry about getting it done.

Over the weekend when driving locally, it became noticeable that the car was losing power when going up a hill and even sometimes between gear changes on the flat.

I had to drop down to 2nd gear to get up a motorway gorge and the hill to home.

There is no noticeable over revving or stalling of the engine, nor is there any blue or white smoke coming from the exhaust.

Any clues/tips as to what might be the problem?

Have you checked the color and level of the transmission fluid?

Car went to Auto Electrician today for inspection.

"Scanned ECM and located code P1320 related to ignition system.

Cleared code but it reappeared.

Removed all 6 coils and plugs visual inspection no evident faults, bunch tested coils, unable to locate faulty part.

Due to previous work done for similar issue, recommended vehicle be returned to previous workshop."

I should add that the motor will only rev to 4k before changing down and is "gutless" in power.

Modified by Zippitynz at 4:17 AM 1/5/2010
Modified by Zippitynz at 4:18 AM 1/5/2010

The shop which replaced the coils did not do a proper diagnostic before and after the coil replacement. And to release the car to you, recommending a transmission flush because of 'sluggish' response is just beyond me. Return the car to their shop and demand a warranty repair. Most shops have at least 30 days warranty.

DTC P01320 indicates Ignition Signal in the PRIMARY CIRCUIT is not sent to the ECM during engine starting/running. Probable cause:-harness or connector between ECM and each ignition coil-condenser-Crankshaft Position Sensor (REF) or circuit.

Since the ignition coils (and plugs) are new and tested OK, those can be eliminated. So we concentrate on the Harness-Connector, Condenser and Crankshaft Position Sensor.

You car is equipped with DIS (Distributorless Ignition System). The Ignition Coil (6 ea.) has a built-in power transistor whose bias (control signal) is provided by the ECM. The coil is powered thru the ECM Relay anytime the Ignition Switch is ON. The Ignition Coil connector has 3 terminals as follows:-Pin 1 (striped wire) - is where the bias signal from the ECM l (@ 0.2VDC with engine at Idle) is connected to alternately turn ON/OFF the power transistor which then enables the spark plug(s) to fire or not. An oscilloscope will provide a better display of coil control signal-Pin 2 (B-Black wire) - is the GROUND connection for the coil. Make sure the engine harness ground points (top of engine, besides intake plenum) are clean and secure. Verify this with ohmmeter (@ 0 ohm if good).-Pin 3 (R-Red wire) - Battery voltage (11-14.7VDC) is connected to this pin and the CONDENSER (top of engine, besides harness) whenever the Ignition Switch is ON. If the voltage is low, the condenser may be leaking or shorted. The condenser acts like a 'shock absorber' for the ignition coil (too complicated to explain at this time). When disconnected, the condenser should read @ 1M-ohm at room temp.

The Crankshaft Position Sensor uses Hall-Effect to monitor the TDC (Top Dead Center) position so the ECM can send the appropriate ignition signal. This sensor is mounted near the crankshaft pulley with a typical resistance of 470-570 ohms.

If you have a multimeter, you can do the testing yourself so you can prove to the shop their botched diagnostic. The Bank 1 coils for cylinders 1-3-5 are on top of the engine, towards the firewall. The Bank 2 coils for cylinders 2-4-6 are towards the radiator and are accessible by removing the engine cover plate.

With Ignition ON (engine not running), check Pin 3 (red wire) of each ignition coil for presence of battery voltage (@ 12.5VDC) w.r.t. chassis GROUND. Each coil MUST have the battery voltage or it indicates problem with the harness/ECM connection. Absence of battery voltage indicates a bad ECM relay or wiring. Low voltage indicates a leaky condenser.

If the required voltage is present in each coil, then start the car and check the CONTROL signal from the ECM. Each Pin 3 (striped wire) should read an average of @ 0.2VDC w.r.t. chassis GROUND. If not, bad wiring or signal from ECM. The presence or this voltage indicates the crankshaft position sensor is working. Again, an oscilloscope, if available, will give a better display of 'firing' signal from the ECM.

Good Luck!

A few hundred dollars later, the culprit turned out to be a faulty air flow meter which has since been replaced.

It is nice to have that feeling of "power" beneath the pedal again

The MAF sensor can be problematic yet does not turn on the CEL most of the time (unless there is an open/short circuit). So testing of the signal output and wiring with a multimeter, better yet with an oscilloscope, will typically show the problem.

loystock wrote:The MAF sensor can be problematic yet does not turn on the CEL most of the time (unless there is an open/short circuit). So testing of the signal output and wiring with a multimeter, better yet with an oscilloscope, will typically show the problem.

Even testing may not show the bad MAF. My co-worker and I both had bad MAFs (Pathfinder and QX4), and both were well within spec according to the voltage tests. Finally changed the MAFs anyway, and power returned to normal for both of us.