Fault Code 42

[89 vn]

Hey, I was wondering if anyone could tell me exactly what code 42 is and how it could be fixed?
42 Open or short on EST or BYPASS line to ignition module

cheers

[YMY-88U]

i had this problem bout a month back and i still dont now if i have fixed the problem. start with the cheapest parts first, so i started with the leads and found that 2 of them had split, so i replaced them. since doing that but i have only driven the car bout 50 meters so still dunno if that has solved the problem. im also bout to buy some msd coils and a new dfi module, so that should definantly clear the problem.

[Cheap6]

Hey, I was wondering if anyone could tell me exactly what code 42 is and how it could be fixed?
42 Open or short on EST or BYPASS line to ignition module

cheers

Assuming that you have fixed the battery terminal problem first.

It can only be:

ECM

DFI

or, perhaps more likely, the wiring linking them, which includes the earth points for the ECM.

Unfortunately, it has nothing to do with the ignition leads, so replacing them won't fix any problem causing a code 42. Sorry guys .

You can perform general tests like moving or (gently) pulling the harness at the DFI and ECM or tapping the ECM case with your fingers and seeing if/when the check engine light comes on or be more specific and look for faults in the relevant wires/connectors, which are:

D4 ECM - white => A at DFI

D5 ECM - tan/black => B at DFI

Code 42 will set if what the ECM expects to see on the wires to D4 or D5 are different to what it has been designed to see.

D4 is the ignition timing signal from the ECM to the DFI, active in "bypass mode", D5 is the signal from the ECM to the DFI to switch the DFI into "bypass mode". An earth or open circuit on the relevant wires can set the 42 because at times the ECM "expects" to see one or the other (the criteria being whether the ECM is signalling bypass mode or not). The open circuit or earth can be within the DFI or ECM, hence they are suspect too.

[PaRaDoX]

ohhh the dreaded code 42 - it killed my car, my car popped one of these the day before i was ment to move house, soo we towed it ended up comming off a trailer during transit..

its usually a issue with the linkage between the CAS and the ecu/coils,
i lied i did fix the code 42 issue but i didnt have enough time to fiddle with it,

i ended up replacing the entire engine loom as that was the easiest thing to do at the time, my old loom got cooked with some retarded timing issues

but the places to start are CAS, coil pack wiring lug and coil packs them self, the error is a general one refers to the ESC not working, kinda hit and miss but look for any cracked wiring plastics

[89 vn]

Im sure the battery and/or the connectors have had it, yesterday my car died and wouldnt start and did the ticking like it had a flat battery my friend came with his v8 and got me going easily but assuming i need a new battery what is a good one to get for a vn v6, my current one is a bosch

[white vn ss]

any had this problem with a vn v8 what are the best places to look?

[Cheap6]

a code 42 will set if there is an issue with the primary side of the ignition system only, so won't be caused by coil. A faulty crank angle sensor will cause a code 41.

If the battery is not good or the terminals are not making a reliable connection that can cause codes to set too, which is why I am suggesting to fix that problem before continuing to look for the cause of the code(s).

A V8 works pretty much the same way with the ignition module performing the same function as the DFI module in terms of how a code 42 is set.

[89 vn]

Ill be replacing the battery on thursday and ill update this thread or make a new one depending on what happened, thanks guys for replies

[Cheap6]

I think that some more info. on how a code 42 is triggered is probably useful. If I put it in this thread ,a search should bring it up close to the top of the list for anyone looking for info. about it.

Ignition systems and the criteria for triggering code 42 are similar for all the Australian models using the 1227808 ECM; L4 in JD/JE Camira and N13 Pulsar/LD Astra; V6; and V8 Commodore, so I‘ll cover all of them. The ignition system is also pretty much the same in VR through to VX, but those models use a cam sensor as well and the fault code numbers have different meanings because the faults can be different.

The ignition modules in L4and V8 are functionally equivalent to the DFI module in V6 with the exception that the DFI module also determines which cylinders receive the spark voltage (each coil fires two cylinders at once; one towards the end of the exhaust stroke, one towards the end of the compression stroke). This function is performed by the distributor cap and rotor button in L4 and V8.

In L4, the ignition module receives a high/low signal from the inductive pick up coil in the distributor each time the magnetic field is generated around it by the timing rotor moving past it. These high /low signals correspond to the ignition event in each of the 4 cylinders ie. two of them occur per crank rotation. In the absence of any input from the ECM, this signal is used by the ignition module to fire the coil without any alteration in timing and the ignition timing is set to 10o BTDC + or - any distributor adjustment away from the factory setting.

The inductive pick up signal is also cleaned up in the ignition module; squared off to give clean high/low voltage transitions, and sent to the ECM on terminal B5. The earth (low) for this signal is via ECM terminal B3, which goes back to the ignition module to be earthed.

When the ECM determines, via the signal across B5 and B3, that the engine is turning faster than 450rpm, it switches a voltage (nominally 5V) onto pin D5, the EST bypass output. When this is received by the ignition module, it is switched into “EST mode”, where the spark timing control is moved to the ECM. The signal output from terminal D4 at the ECM is then used as the ignition trigger. In the absence of the pin D5 voltage, in “Bypass mode”, engine rotating below 450rpm, such as occurs during cranking, the EST output (D4) is simply earthed by the ignition module.

In V8, the distributor uses a Hall effect sensor instead of the inductive pick up and the ignition module is of a different design but otherwise it is functionally the same as the that in L4. The Hall sensor switches 4 times per crank rotation, required for the firing frequency of a 4-stroke V8, with the Hall effect sensor signal corresponding to the cylinder being fired, again 10o BTDC + or - distributor adjustment.

In V6, the information about crank position and velocity is provided by the two Hall effect sensors on the nose of the crankshaft; collectively the “Crank Angle Sensor“. One sensor switches high-low V (open circuit-earth) 18X (= one high for 10o + one low for 10o) per crank rotation, the other sensor , the 3X sensor, switches high-low V with 10o, 20o, and 30o low signals corresponding to each of the three crank positions with pistons on the compression stroke (and simultaneously exhaust stroke on paired cylinders).

The 3X signal is only used by the DFI to determine when to fire each coil, by counting the number of 18X signals per 3X high-low, when the engine is initially started, then ignored. The DFI also divides the 18X signal by six to give a signal sent to the ECM across B5-B3 that occurs 3 times per crank revolution ie. the equivalent to that which occurs naturally with L4 and V8 from the distributor pickup or sensor. In Bypass mode, once again ignition timing is set to 10o BTDC.


Code 42 is set:

If while voltage is not switched internally by the ECM to terminal D5 (in Bypass mode) the output from D4 is not earthed. This can occur if the wiring connection between the ECM D4 terminal and the corresponding terminal at the ignition/DFI module is not made (open circuit) or an internal fault causes the same in the ECM or DFI.

Alternatively, with voltage switched internally by the ECM to terminal D5 (in EST mode), D4 remains earthed. This would be caused by a short to earth on the wiring connection between the ECM D4 terminal and the ignition/DFI module or an internal module or ECM fault. The code will also set if the connection between D5 and the module is not made, whether by a broken D5-module wiring connection (open circuit), a short to earth on the D5-module wiring or an internal ECM or module fault.


To test:

All these tests require that the fault is continuous. If it is intermittent, you are back to the “wiggle wiring harnesses and tap ECM” test method or guessing.

The ECM terminal numbers, D4, D5 etc. are cast into the plastic connectors at the ECM. A dressmaker‘s pin inserted into the ECM harness connector terminals works well to make an electrical contact without damaging them.

Disconnect the ECM terminal connectors and turn the ignition on.

An Ohmmeter between the wiring terminal to D4 in the connector to the ECM and an earth should show that it is earthed, hopefully by the ignition/DFI module. If it is not earthed, there is an open circuit in that wire somewhere, the ignition/DFI module isn’t earthing the circuit properly internally (faulty module) or the connection between module and harness isn‘t good. Each of these possibilities can be checked using the Ohmmeter to the appropriate terminals with the harness connector disconnected from the module.

The bypass switching can be checked with a test light connected between battery voltage and the terminal to D5 in the connector to the ECM, which goes to the ignition/DFI module bypass input. The test light should not light (the resistance on this circuit in the module is high) - which checks the D5 circuit is not earthed. If it does light, disconnect the connector to the module and recheck. If the light stays on, the wire between D5 and the module is shorted to earth. If it goes out, the module is faulty.

If the test light does not light, because voltage is being supplied via the test light to the D5 circuit, the Ohmmeter on D4 to earth should change while ever the light is connected to the D5 terminal, to indicate an open circuit. If the Ohmmeter, between the D4 connector terminal and earth, doesn’t indicate a switch to open circuit and the test light doesn’t light, either the module isn‘t working, the D5 circuit is open circuit (including the possibility of a poor module-harness connection) or D4 is shorted to earth between the ECM and module.

To determine which, disconnect the other end of the wiring harness (connector) from the ignition/DFI module and check with the Ohmmeter. If the D5 wire is OK, the D4 wire is not shorted to earth and the switch to open circuit on D4 didn‘t occur then it is the ignition/DFI module that is dead.

If all that checks out OK, the ECM or ECM harness connector must be at fault.


A mention of how code 41 is set may be relevant too. Code 41 is only applicable to V6 and V8. It is set when the ECM receives data indicating the engine is being cranked and no signals are received across B5-B3. The criteria are, with no B5-B3 signal, battery voltage is less than 11V, as occurs with the starter motor drawing current and, with no MAP sensor fault codes active, the MAP sensor indicates 3kPa below ambient, suggesting the engine is turning and pulling in air.

[va23boam]

where exactly do you find error codes? does it involve plugging your ecu into a computer?

[Cheap6]

where exactly do you find error codes? does it involve plugging your ecu into a computer?

With an interface cable (About $15 in parts, software (eg. WinALDL) is shareware. There's a "How To" on here) you can connect your car's computer to a PC or laptop which will give you all the sensor readings (at a fairly slow sample rate).

http://forums.justcommodores.com.au/...commodore.html

The codes can also be extracted with a wire or paper clip:

http://forums.justcommodores.com.au/...lts-vn-vp.html

[MyVPIsFasterThanYourVP]

cant you just use a paper clip and read the flashing engine light for the codes like it says in the gregorys?

[vn calais manual]

^^ yeah, thats the easiest way to do it. mate