Going back 9 years in my search for answers to the same question, I stumbled on many similar threads where the final resolution to the original problem is never posted. I hope someone can help:
- SES light out of the blue...
- DTC Code: P0237 (MAP Sensor Signal Return Circuit A low... less than 0.04v)
- Cleared code with NGS, and it immediately reappears in less than a second (25ms polling rate).
- Visually checked wiring, which was protected in doubled up heat resistant protective loom.
- In the 2000, 01, 02, & 03 PCED manuals, PinPoint test DH6 for DTC P0237 calls for less than 5 ohms resistance between the disconnected MAP sensor harness connector at Signal Return Circuit 359 (Gray w/ Red stripe) and ground, with Key ON
, engine off. With a Fluke 87, I measured 771,000 ohms to the nearest firewall ground point, and 841,000 ohms directly to the nearest negative battery terminal.
In the 1999 PCED, PinPoint test DH6 calls for less than 5 ohms resistance between the disconnected MAP sensor harness connector at Sig. Ret. Cir. 359 (GY/R) and ground, with Key OFF
. I measured 0.8 ohms to the nearest firewall ground point, and 4.5 ohms directly to the nearest negative battery terminal.
- I have a 2000. The 1999 PCED makes more logical sense, due to the results of OTHER TESTS PERFORMED (see below). But since I have a 2000, I don't know what to believe. Some things change, some things stay the same. For example, there was a change between 1995 and 1996 with respect to the MAP signal wiring and the PCM. There was also a change between 1997 and 1999 in MAP signal wiring (moving from PCM pin 34 to pin 79). There was also a major wiring change between 2001 and 2002, but I don't believe that wiring change effected MAP signaling. There is also such a thing as typos. It could be that when the 1999 PCED was updated to 2000, a typo was made and missed, that carried forward to successive years. There is also such a thing as evil. It could be that when Ford was required by the EPA to make PCED manuals open source and free, they put a few puzzles in there to keep the independent shops puzzled and the Ford dealer service departments in business. I know, I'm reaching here, but I am in the puzzled camp right now. The 1999 PCED pinpoint test came from a paid for print, and the other years were checked for free online. Sigh.
OTHER TESTS PERFORMED (All PASSED) :
- DH7 Voltage REF Circuit 351 Brown w/White stripe was indeed 5.1 volts. Tested at MAP harness connector (with MAP sensor disconnected)
- DH8 Continuity between Circuit 358 Green w/Black stripe and PCM test Pin 79 was indeed less than 5 ohms... actually 0.6 ohms to be exact. Ford 104 pin breakout box used for this test, with PCM connected.
- DH9 No shorts to ground found between PCM test Pin 79 and case ground, power ground, and all other grounds at PCM pins 25, 51, 76, 77, 91, & 103. Breakout box (BOB) used with PCM disconnected, as instructed.
- With Key ON, Engine OFF, I measured voltage between pins 90 VREF and 91 Signal Return Ground, and found 5.1 volts as expected.
- With PCM disconnected, I measured resistance between Circuit 359 Signal Return and Pin 91, and found 0.1 ohm resistance. To my mind, this means that there is no physical problem with that Gray & Red wire (the one that measured 800,000 ohms in DH6).
And THIS is why I suspect that the PCED for 2000-2003 might be in error for Pinpoint test DH6.
However, I still have DTC P0237, which is what started all this in the first place.