Hey All, been getting this old field find FD backup and running as my new daily. Its been completely rebuilt and street ported, running Haltech with the 13b terminated engine harness. I no longer have the stock oil pressure sending unit but I'd love to get the oil pressure working on my stock cluster. Has anyone ever used outputs from Haltech to drive oil pressure? I spoke to SevenSins about this and it seems like its not possible but I thought I'd ask the hive here if anyone has been successful.
My other options seem to be:

• Run a splitter for the oil pressure and reintroduce my stock Oil pressure sensor
• Do some hacking on the stock cluster so I can mount the Haltech Multi function CAN Gauge and just pull straight from ECU (I don't like this option)

I'm not a fan of gauge pods and really want to keep the stock cluster.....stock. Only current after market gauge I run is AFR and its mounted in the radio din.
I did do some searching but didn't find an exact thread for this, just build threads where oil pressure is mentioned. Thanks in advance!

 

Yes, you can drive the gauge from any pwm output that is capable of current sinking. (An analog output capable of linear current sinking will also work) You will have to sort out the calibration values to get the correct scale; span and zero, but the gauge is reasonably linear, iirc.

I did this a long time ago so that I could use the gauge to display other values, e.g., boost, discretely. It works fine. I also graphed the gauge’s response at the time, if I can find that info, I’ll post it up here.

 

Do I just enable a generic output? Any idea what signal type? I only have Duty Cycle, Frequency, State, Current, 4 wire stepper and 6 wire stepper. Thanks by the way!

 

Google answered my question, Yes generic output and Duty Cycle is what I need I believe.

 

About the only thing you can do is run the factory oil pressure sensor to the factory cluster.

The Oil Pressure Switch is a simple "dual" on-off switch. It uses 12V and ground. It is also located on the Engine harness (bit of a misnomer as it is not what most would consider the engine harness) as Mazda calls the harness that does everything for the engine the Emissions Harness.

So even though you have a different wiring harness to control your injectors, coils, etc., the connection for the oil pressure switch is located on a separate harness.

Reading true oil pressure requires a proper sensor (which are 5V with 0V ref), and the dash one, really is more for show than anything else at this point in technology.

 

That's been my understanding. I am currently using a Low Dollar motorsports pressure sensor for my oil pressure for Haltech. I really want to use that sensor through haltech to power the gauge. I'm going to try it using an output set to Duty Cycle from haltech to the Gray/Red wiring feeding the gauge and see what happens.

 

^^ Yep, you’ve got it. Use the duty cycle settings for the zero point and to calibrate your range. Increasing duty (on time) will move the gauge upscale. You only need to set the frequency high enough that you don’t have any pulsating in the needle; shouldn’t take much since the gauge has a relatively long integration period.

 

Sick! Thanks Speed! I have my cluster out at the moment waiting for a few capacitors to fix my speedo. Once I have that done and back in, I'll test this out and report back. Maybe I'll make a clear guide for getting speedo, tach and oil pressure working. Its not super obvious when using the 13b terminated harness(as it replaces the stock harness which if removed also removes the x-14/emissions harness) so maybe it will help someone else.

 

This is very interesting.... So you're basically saying you can drive the dash oil pressure gauge with a spare PWM/duty cycle output that can sink some current from any aftermarket ECU? Which is basically how we use an aftermarket ECU to drive the tach.

Like lots of folks, my FD's OEM oil pressure sender is failing - I get pretty erratic readings on the dash gauge; I'm also running a Link G5 NEO4 ECU with its own 0-5VDC oil pressure sender, so I have an accurate reading of oil pressures from that, and can display them on a GaugeART CAN bus gauge. But I'd really like the dash gauge to work - I hate inoperative crap! Initially I was either going to get another OEM sender from Ray Crowe, or better yet, find a more reliable substitute sender - which caused me to characterize the sender ohms vs. dash oil pressure reading by using a decade resistor substitution box (emulates the OEM sender).

For anyone interested, here's the resistance values I measured with the resistance substitution box for the OEM sender vs. my FD's dash gauge reading:

0 psi tick on gauge = 61 ohms
30 psi tick on gauge = 41 ohms
60 psi tick on gauge = 25.6 ohms
90 psi tick on gauge = 10.2 ohms
120 psi tick on gauge = 4.7 ohms

Since I've got LOTS of spare PWM/duty cycle capable outputs on my Link ECU, the thought of driving the dash oil pressure gauge with the Link instead of the OEM sender is very appealing. Will need to dive into the FD schematic to figure out how to best wire it though. Physically, my Link is located where the OEM ECU was, so unless one of those "X" connectors in that area (e.g., X05, X14) has the oil pressure signal from the OEM sender available, getting that output from the Link to the dash may be a bit more difficult.

Edit: Just checked the FSM, the Gy/R wire for the oil pressure gauge can be tapped at X12 (Gray connector in the engine bay) or X06 (Blue connector, LHD driver's side footwell, near fuse box). So easiest option for me is to run a new wire from the Link (pass. side kick panel area) across to the driver's side to connect to Gy/R in X06. Too bad it's not in X14 with the dash coolant temp gauge wiring, that would have been much easier!

 

I can confirm it worked! The output wire is used was already in my engine bay so I just plugged into the factory temp sensor plug in the bay. The duty cycle frequency it likes is around 150Hz, my table still needs a little tweaking but it seems to work pretty good! Its reading a smidge low here, its actually about 40psi according to haltech. Now I just need to get my damn speedo figured out (my guage doesnt work, its not the wiring or capacitors).

 

Thanks, good to know I can pitch the flakey OEM oil pressure sender and still have a working dash gauge! I figured out how I'll wire mine in - since I'm running IGN1A coils and the OEM ignitor is gone, there are about 4~6 unused wires in the front harness that go between the <B1-01> (OEM ECU connector) and <B1-09> (ignitor connector). So I can shunt one of those unused wires at <B1-09> to the OEM oil pressure sender wire connector <C1-05>. On the ECU end, I'd just connect a spare AUX output to the 12 pin DTM connector I use to tap OEM circuits from <B1-01>. Used a similar wiring scheme to add a fuel vapor purge solenoid valve that my Link controls.

 

Hell ya! Glad we got this figured out! This thread is why I miss car forums so much. Big thanks everyone, especially @Speed of light !!

 

Well I got my dash oil pressure gauge working with my Link G5 Neo4 driving it! Similar to the Haltech setup, I wired a spare AUX output to the oil pressure gauge, basically disconnected the Gy/R wire from the stock oil pressure sender, and connected it instead to my spare AUX output. My initial calibration & testing using the same 150Hz frequency others have used made my gauge a bit noisy, and difficult to calibrate - small changes in DC would give large swings of the needle, But raising the constant frequency to 1KHz solved that problem. Here's a screen shot of the Link G5 settings that worked for me:


So for the Link guys, what I'm doing here is setting up AUX4 as a General Purpose PWM (GP PWM) output. The condition that activates the PWM output is simply battery voltage > 12V. From there, it PWM pulses a low side output at a constant frequency of 1000Hz, its Duty Cycle (DC) determined by the 2D control table as a function of oil pressure. During calibration, I adjusted DC so that the needle would rest consistently on the gauge's tick marks at 0, 30, 60, 90 and 120 psi without making noise.

 

Nice, in theory this should also work for coolant? the haltech harness omits the coolant wire (for the gauge) in the engine bay. Was planning wiring it to x14 but might be easier to use the haltech temp sensor and send to Dash...... And yes please make a guide RE Speedo/tach/Pressure driven by haltech.